| What are the main scalar and vector quantities? | The main scalar quantities are
MEDSTT
mass
energy
distance
speed
temperature
and time.
While the main vector quantities are DAMWFV
displacement
acceleration
momentum
weight
force
and velocity |
| What do scalar or vector quantities have? | Scalar quantity it must only have magnitude, they do not have a direction. While vector quantities have both magnitude and direction. |
| What are the main vector quantities? | The main vector quantities are DAMWFV
displacement
acceleration
momentum
weight
force
and velocity |
| What is a force? | A force is a push or a pull that acts on an object due to an interaction with another object. |
| What is a contact, non-contact and normal contact force? | Contact forces are when two objects are physically touching. E.g. air resistance when air particles collide with a parachute, and friction that happens when an aeroplane lands on the sea, which cause it to slow down.
Non-contact forces are when two objects are physically separated, e.g. the electrostatic force, which is the force between two charged objects.
While a normal contact force is when two objects are in direct contact and both forces exert a force upon one another, e.g. an aeroplane flying through the air or a book on a table. |
| How do electrostatic forces act? | Objects with opposite charges experience an electrostatic force of attraction whereas objects with the same type of charge have an electrostatic force of repulsion. |
| What is the resultant force? | The resultant force is a force that has the same effect as all of the original forces acting together. And the resultant force can be calculated by subtracting the smaller force from the larger force. Although if there is more than one force acting no on the object add all the force going left, and all the forces going right. Then subtract the smaller force from the larger force. |
| What is the resultant force when the forces acting on an object are balanced? | When the forces acting on an object are balanced or equal, the resultant force is zero. |
| What does the length and direction of the arrow show in free body diagrams? | In free body diagrams, the length of the arrows shows the size of the force, and the direction of the arrow shows the direction of the force |
| What do the terms altitude, lift and thirst mean in free body diagrams? | In free body diagrams the altitude refers to the height above the ground.
Lift refers to a force with the same magnitude as the object’s weight that acts in the opposite direction to the weight.
And the thrust refers to a forward force. |
| What is a vector diagram? | A vector diagram is a scale drawing that shows the forces involved in a given scenario. And in vector diagrams the object is represented by a dot or small circle. |
| Give the steps to drawing a vector diagram when once force has a magnitude of 10N, the other force has a magnitude of 8N and the angle between the forces is 30 degrees | First draw the object as a dot, and draw a 10cm long arrow to represent the 10N force. Using a protractor measure an angle of 30 degrees. Now draw an 8cm arrow to represent the 8N force.
Now to create a parallelogram copy the 8cm line and position it at the head of the 10cm force vector. Use a protractor to double-check the angle is still 30 degrees. Then copy the 10cm line and position it at the head of the 8cm force vector.
Now draw a straight line from the tails of the force vectors to the other side of the parallelogram.
Finally measure the length of the vector (straight line) and this is the resultant force. |
| How can you take a single force and resolve it into two components? | To take a single force and resolve it into two components, measure the given angle, and draw the diagonal force. Because the diagonal force acts both vertically and horizontally, or in both the y and x direction, it will give the two components of a vertical or y acting, and a horizontal or x acting force. |
| When is work done? | Work done is done whenever a force used to move an object causes energy to be transferred. And work done is calculated using the equation, Work done (J) = Force (N) x Distance (m), where the distance must be in the line of action of the force. Although the unit newton-meter may be used instead of Joules and 1 newton-meter of work = 1 joule. |
| What energy changes take place when a car breaks and what energy changes take place when a man pushes a force? | When a car breaks the break presses against the wheel, the force of friction between the tire and the road now acts between the break and the wheel. As all moving objects have a kinetic energy store, the car’s kinetic energy store is transferred to the thermal energy store of the breaks. Therefore the temperature of the breaks increases while the car slows down and loses kinetic energy.
When a man pushes a box, the man applies a forward force on the box but the force of friction acts between the bottom of the box and the floor. This friction causes the temperature of the box to increase. Therefore in this energy transfer, the chemical energy store in the man’s muscles has been transferred to the thermal energy store of the box. |
| What energy changes take place when a person walks up a staircase? | When a person walks up a staircase they move upwards, against the force of gravity, given that the force of gravity acting on a person is their weight e.g. 600N. Therefore the person’s chemical energy store is transferred to the gravitational potential energy store when they reach the top of the stairs, where they have moved a vertical distance of 5m, from the floor. Given that the distance must be in the line of action because weight (force) is acting vertically downwards only the vertical distance is relevant in this example. |
| What are elastic and inelastic deformation? | Elastic deformation is when a material experiences a force that changes the shape or length, but when the force is removed, the material returns to its original shape or length. Therefore inelastic deformation is when an object experiences a force that changes the shape or length, but when the force is removed, the material will remain deformed. And inelastic deformation can be seen in certain polymers. |
| What is the equation to find the force needed to stretch an elastic material? | The equation used to find the force needed to stretch elastic materials is: Force = spring constant x extension/compression. |
| When is work done on an elastic material? | Work is done on an elastic material when a force is used to stretch or compress the material. And in this case, elastic potential energy is stored in the object, and the work done = elastic potential energy, given that the material is not inelastically deformed. |
| What do you do in the spring extension practical? | First set up a clamp stand, two bosses and two clamps. Now place a heavy weight on the clamp stand to stop it falling over. Next, attach a spring in the first clamp and a meter rule in the second.
Ensure the top of the spring is at the zero point on the meter rule. The meter must also be vertical to avoid inaccurate readings. And the bottom of the spring has a wooden split attached as a pointer, that must be horizontal to avoid inaccurate readings.
Now read the position of the pointer on the meter rule. This is the unstretched position of the spring (the length with no force attached).
Next hang a 1m weight on the spring. Read the new position of the pointer on the meter rule.
Continue adding 1N weights on the spring and reading the position of the pointer. Then these readings to work out the extension |
| How are the readings on the meter rule used to work out the extension? | To use the readings on the meter ruler to work out the extension, subtract the unstretched position from each reading. E.g. if the unstarched position was 30cm and the extension produced by 1N weight is 34, the reading for 1N would be 4 cm. Then plot the extension against the weight. |
| How can you work out the weight of a mystery object? | To work out the weight of a mystery object e.g. a stone, draw a horizontal line to measure the extension produced by the stone, and from the end of this line, read the weight of the stone or the y value. |
| What are linear and non-linear relationships? | Linear relationships are where the extension and force produce a straight line of results e.g. in directly proportional relationships. While non-linear relationships are where the line of results is not a straight line. |
| What does the graph for the spring show? | The graph for the spring shows a straight line of results passing through zero. This shows the extension is directly proportional to the weight. Therefore the relationships between the extension and force are linear. This graph also proves the spring is elastic because if the weight is removed the extension returns to zero. Although if too much weight is added the graph will curve upwards at the end and become non-linear. The spring has been overstretched and exceeded the limit of proportionality. Therefore it has been inelastically deformed and cannot return its original shape if the force is removed. |
| How is the spring constant found in extension/force graphs? | In extension/force graphs the spring constant is extension / force (weight). |
| What do direction and displacement show? | Distance only shows how far an object moves. But displacement shows the distance an object moves from the start point to the finish point. And displacement must include the direction of that straight line. |
| What is the normal walking, running, and cycling speed and what does it depend on? | Important speeds to remember include:
The normal walking speed I 1.5m/s.
The normal running speed is 3m/s.
And the cycling speed is 6m/s.
Although the speed can depend on age, as a younger person may be able to move faster than an older person, terrain as people tend to move more rapidly on flat ground than moving uphill, and distance, as people tend to move faster at the start when they are less tried. |
| What are some other important speeds to remember? | Other important speeds to remember are:
Car on a main road – 13m/s
Fast train in the UK – 50m/s
Cruising aeroplane – 250m/s
And Speed of sound in air – 330m/s
Although the sound of speed can vary e.g. sound travels faster on warmer days than on cooler ones. And the speed of a moving object is rarely constant as a car will speed up and slow down over a journey, but average speeds are used to make calculations easier. |
| What do the speed, velocity, and acceleration show? | The speed shows the distance an object travels at a given time. And is calculated using: Speed = Distance / Time.
The velocity shows the speed of an object in a given direction e.g. an object travels at 20m per second, South. And the velocity is calculated with the same equation used for speed, although the direction is also stated e.g. 1.25m/s
South.
The acceleration shows the change in the velocity of an object over a given time. And acceleration (m/s^2) = change in velocity (m/s) / time (s), where the direction is also stated. |
| What happens if an object moves at a constant speed in a circle? | If an object moves at a constant speed in a circle, its velocity is constantly changing even though its speed is constant. This also accounts for an object travelling around part of a circle e.g. a corner. |
| What does the gradient of a distance-time graph show? | The gradient of a distance-time graph shows the speed. Therefore the gradient is calculated using distance travelled/time taken. |
| How is the speed of a curved slope calculated? | The speed of a curved slope shows the speed is constantly increasing, it is accelerating. Therefore to calculate the speed place a dot the given point e.g. 100s, then draw a large tangent to the line. And finally workout the gradient by making the tangent a right-angled triangle. |
| What shows the acceleration in a velocity-time graph? | The gradient of a velocity time graph shows the acceleration of the object. As an upwards slope shows the object is accelerating, while a downwards slope shows the object is decelerating and a horizontal line shows a constant velocity or speed. Acceleration is calculated using the equation:
Acceleration (m/s^20) = final velocity (m/s) – initial velocity (m/s) / time (s) |
| What is the area under a velocity-time graph and how can the total area be calculated? | The area under a velocity-time graph is the distance travelled in a specific direction – the displacement. And when the distance travelled has a constant, acceleration of deceleration, the graph can be divided into shapes e.g. triangles and rectangles/squares to calculate their total area.
But when velocity-time graphs have accelerations and decelerations that are not constant, but rather curved lines, work out the total area under the graph by counting the number of squares. Then add the total of the parts (halves and quarters) of squares to include the total area. |
| What is the equation for an object that accelerates at a constant rate? | The equation for an object that accelerates at a constant rate is:
V^2 – u^2 = 2as
final velocity^2 (m/s) – initial velocity^2 (m/s) = 2 x acceleration (m/s^2) x distance (m) |
| What changes take place when a skydiver jumps out of the plane? | When a skydiver or any object falls towards the surface of the Earth, it initially accelerates to around 9.8m/s^2. This acceleration is due to the force of gravity acting on the object.
As the skydiver falls, he experiences air resistance or an upward force of friction with the air particles. And after some time the force of air resistance balances the force due of gravity. At this point, the skydiver stops accelerating and moves at a constant velocity. And this applies to any object falling through a fluid, in this case, the fluid is air.
The terminal velocity the skydiver reaches depends on the object. Some objects experience a greater force of friction due to their shape so they will have a lower terminal velocity. |
| What is the air resistance, and terminal velocity? | Air resistance is the force of friction with air particles.
Terminal velocity is when an object stops accelerating and starts to move at a constant velocity. |
| What is Newton’s First Law of Motion? | Newton’s First Law of Motion is if the resultant force acting on a stationary object is zero, the object will remain stationary.
And if the resultant force acting on a moving object is zero, the object will continue moving in the same direction, at the speed/velocity. |
| Prove Newtons First Law of Motion in terms of the movement of a stationary object. | When a stationary object has no forces acting on it, there is no resultant force. So the object will remain stationary. While when an object has a 50N force acting to the right and another 50N force to the left, because the forces are balanced, the resultant force is zero. Therefore this object will also remain stationary.
While in terms of velocity, as the stationary object has no forces acting on it, its resultant force is zero. So the speed and direction of the force will stay the same. So the object will continue to move with the same velocity. And as the object with a 50N force on the left and the right, has a resultant force of zero, the force of speed and direction will also stay the same. So it will continue moving at the same velocity. |
| When will the velocity of an object only change? | The velocity of an object will only change if a resultant force is acting on the object. |
| What happens when a car drives at a constant speed? | When a car drives at a constant speed, the driving force of the engine is acting to the left. While because the car is moving at a constant speed, there needs to be an equal force acting to the right. And these forces that oppose the motion of the body are called resistive forces. In this example, the resistive forces are friction with the air and friction with the road. Although in general, resistive forces include friction, viscosity and drag, where drag is the resistance of an object’s motion through a fluid. |
| What happens when a resultant force acts on a stationary and moving object? | A resultant force of 50N is applied to the right of a stationary object. This causes the object to accelerate to the right. Therefore a resultant force causes an object’s speed to change.
An object is moving at a constant speed to the right. A resultant force of 50N is applied to the left. This causes the object to decelerate (slow down), therefore also causing the speed to change.
A resultant force can also change the direction of speed. When an object is moving at a constant speed and a resultant force is applied to the bottom of an object, the object accelerates upwards. |
| What is Newton’s Second Law of motion? | Newton’s Second Law of Motion is the acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass of the object. |
| Demonstrate Newton’s Second Law of Motion. | Two objects have the same mass, and both experience a resultant force. The top object experience a resultant force of 20N to the right, and the bottom object experience a resultant force of 10N to the right. Given that the acceleration is proportional to the resultant force acting on the object, a greater force gives a greater acceleration. Therefore the top object will experience a greater acceleration that the bottom object.
To prove the acceleration of an object is inversely proportional to the mass of the object:
Two objects both experience a force of 20N. The top object has a mass of 1kg and the bottom object has a mass of 2kg. Given that the acceleration is inversely proportional to the mass of the object if the mass is larger the acceleration will be smaller. Therefore the top object will experience double the acceleration of the object. |
| What is the equation for the force needed to accelerate an object? | The equation for the force needed to accelerate an object is Force (N) = Mass (kg) x Acceleration (m/s^2). |
| What are the speeds, accelerations and forces involved in car transportation? | A car travels at a speed of 13 m/s on a main road, and 30 m/s on a motorway.
To accelerate from the main road to a motorway, a car experiences an acceleration of 2 m/s^2.
And for a typical family car, that would require a force of 2000 N. |
| What are inertia and the interrail mass? | Interna is another way to phrase Newton’s First Law. Inertia means an object will stay stationary or continue moving at the same speed and direction (velocity) unless a resultant force is applied.
While the interrail mass is a measure of how difficult it is to change the velocity of an object. And the inertial mass is defined as the ratio of the force needed to accelerate an object: the acceleration produced. Objects with a larger inertial mass will require a large force to produce a given acceleration than objects with a smaller inertial mass. |
| What is Newton’s Third Law of Motion? | Newton’s Third Law of Motion is whenever two objects interact, the forces they exert on each other are equal and opposite. |
| What are four examples of Newton’s Third Law of Motion?
. | An example of Newton’s Third Law of Motion is canoeing. When a person uses a paddle to push the on the water, the water pushes back on the paddle. This force is a lift, meaning it is equal in magnitude to the object but acts in the opposite direction.
When a girl jumps off the skateboard she applies a push force onto the skateboard. This causes the skateboard to move to the right. At the same time, the skateboard pushes back onto the skateboard. And this force is equal in magnitude but opposite in direction, and this causes the girl to move toward the left.
When a rocket fires, the chemical reaction produced a downward push force on the hot exhaust gases. The hot exhaust gases exert an equal force on the rocket but act in the opposite direction, upwards.
When a car is driving the wheel exerts a force in the reverse direction on the road. At the same time, the road exerts a force in the forward direction on the wheel. These forces are equal in magnitude but opposite in direction |
| What do you do to investigate the acceleration of an object? | To investigate the acceleration of an object, on a desk draw chalk lines of equal distances e.g. every 10cm.
Then on the desk attach a toy car to a string. The string is looped around and pulley and the other end of the spring is attached to a 100g mass. The weight of this mas provides the force acting on the toy car. And a timer is needed.
Hold the toy car at the starting point. When ready let go. Because there is a resultant force acting on the string, the car will accelerate along the bench.
Record the time taken for the car to pass each distance marker.
Although if the car is moving rapidly it would be difficult to record an accurate time. To record the times more accurately record the experiment on a phone, so the experiment can be played back.
Then repeat the experiment several times. Each time decrease the weight on the string e.g. 80g, 60g, 40g and 20g. |
| What is the object in the acceleration of an object practical? And why is it proportional? | This practical investigates the effect of changing the force on the acceleration of an object while keeping the mass of the object constant. Although the object is not just the toy car. It is the toy car, the string, and the mass on the end of the string because they are all attached. And this means if the mass is removed from the end of the string, it needs to be transferred onto the toy car. This keeps the overall mass of the object the same.
As the resultant force is the weight of mass on the end of the string, the acceleration of the toy car would be proportional to mass on the other end of the string. This is because Newton’s second law of motion states the acceleration of an object is proportional to the resultant force acting on the object. |
| How do you investigate the effect of the object’s mass on the acceleration produced by a constant resultant force? | To investigate the effects of changing the object’s mass on the acceleration produced by a constant resultant force, attach a 100g mass to the end of the string. Then attach a 200g mass to the toy car.
Record the car as it acerates along the bench.
Now repeat the experiment, increasing the mass attached to the toy car.
Newton’s third law states the acceleration of an object is inversely proportional to the mass of an object. Therefore as the mass of the toy car increases the acceleration should decrease. |
| What is the stopping distance? | The stopping distance is the total distance travelled from when the driver first spots the obstruction e.g. a child, to when the car stops. And the stopping distance can be divided into two parts. The thinking and the braking distance. The thinking distance is the distance travelled by car during the driver’s reaction time. The reaction time is the time taken for the driver to spot the obstruction, make a decision, and move their foot to the break. And the braking distance is the distance the car travels from when the driver applies the breaks to when the car stops. Although the stopping distance will be greater when the speed of the vehicle is greater (assuming the same braking force is applied). |
| What is the stopping distance for a typical family car? | The stopping distance for a typical family car, travelling at 30mph is 23m. The equivalent length of six cars. |
| What is the average reaction time? | The reaction time varies from person to person. But a typical range is between 0.8 to 0.9 seconds. A person’s reaction time can be measured using a ruler. To do this one person holds the ruler, and a volunteer places their fingers beside either side. The ruler is then dropped the volunteer has to catch it. The further the ruler falls, the longer the reaction time. And by measuring the distance the ruler fell, the reaction time can be looked up in a table. |
| What affects a driver’s reaction time and stopping distance? | If a driver is tried their reaction time will be longer than a driver who is alert. Alcohol and certain drugs can make the reaction time longer. Distractions in the car, such as a smartphone, will also increase a driver’s reaction. And because all of these factors increase the reaction time they also increase the thinking distance.
A driver’s stopping distance can be stopped by wet or icy conditions, worn tires and brakes. This is because wet or icy conditions reduce the friction between the tyres and the road, increasing the braking distance. Worn tyres increase the stopping distance because they reduce the friction between the tyre and the road. And work brakes also increase the braking distance. |
| What does the kinetic energy depend on? | Because kinetic energy = ½ mass x velcoity^2, the kinetic energy depends on the velocity^2. So if the velocity of a car is doubled, the kinetic energy quadruples. And when a car breaks and comes to a stop all that kinetic energy is converted into other forms of energy. |
| What does the greater the speed, the greater the braking force needed to stop the car mean? | The greater the speed, the greater the braking force needed to stop the car. This means if a driver is travelling at high speeds and needs to brake, they need to apply a very large braking force. A large braking force will cause the car to decelerate rapidly. But it will also cause a large amount of kinetic energy to be transferred to thermal energy in the breaks. This can cause the brakes to overheat and cause the driver to lose control of the vehicle. |
| How do you estimate the forces involved in the deceleration of vehicles on public roads? | To estimate the forces involved in the deceleration of vehicles on public roads, use the equation: Forces (N) = Mass (kg) x Acceleration (m/s^2). And substitute the Acceleration for the deceleration. |
| What do all moving objects have? | All moving objects have momentum. But if an object is not moving, its momentum is zero. |
| What does the conversation of momentum refer to? | The conversation of momentum is: When a system is closed, the total momentum before an event is equal to the total momentum after an event. E.g. A van travels towards a stationary car. Because the van is moving, it has momentum in the forward direction. The momentum of the van is its mass x velocity. While the stationary car has no momentum and is not moving. But if the van collided into the car, both the van and the car would move together at a lower velocity than the initial velocity of the van. In this system of the van and car, the total moment is now the same as the initial momentum of the van alone. Therefore the total moment before the collision is the same as the total momentum after the collision. Ergo, momentum has been conserved. |
