Physics
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| 🇬🇧 | 🇬🇧 |
| How do you calculate average speed? | ...................................Distance Average Speed = ---------------------- ........................................Time |
| Define Displacement | Distance moved by object in a particular direction |
| How do you calculate velocity? | Change in displacement ------------------------------ Time taken |
| How do you calculate change in displacement? | Velocity x Time taken |
| How do you calculate change in time? | Change in displacement --------------------------- velocity |
| The slope of a displacement-time graph tells us how fast an object is moving. The straight line shows............ | The straight line shows that the object's velocity is constant |
| The slope of a displacement-time graph tell us how fast an object is moving. The slope shows which object is moving faster. The steeper the slope the............... | The steeper the slope the greater the velocity |
| The slope of a displacement-time graph tell us how fast an object is moving. When the slope of the graph is 0. What does this tell us? | - Displacement is not changing - Hence velocity =0 - Object is stationary |
| The slope of a displacement-time graph tell us how fast an object is moving. When the slope of the graph suddenly becomes negative, what does this mean? | The object is moving back the way it came |
| The slope of a distance-time graph tells us how fast an object is moving. The displacement-time graph is curved, what does this tell us? | - The slope is changing - Means object's velocity is changing |
| What is the formula for Subtraction of vectors? | A - B = A + ( - B ) |
| What is the formula to calculate average speed | ...................................DISTANCE Average speed = ---------------------------- .......................................TIME |
| Acceleration of something indicates what? | Acceleration of something indicates the rate at which its velocity is changing. |
| Acceleration is defined as? | Rate of change of velocity |
| What is the formula we use to find average acceleration? | Change in velocity ------------------------ Time taken |
| Units of acceleration is | M s^-2 Meters per second squared |
| The gradient of a velocity-time graph is equal to acceleration. What does a straight line with a positive slope show? | Constant acceleration |
| The gradient of a velocity-time graph is equal to acceleration. So, greater the slope,... | Greater the acceleration |
| The gradient of a velocity-time graph is equal to acceleration. If the slope is changing: | The acceleration is changing |
| Displacement = area under velocity-time graph. In the case of a triangle what is the formula | 1/2 x base x height |
| Explain how using light gates we can measure acceleration Give formula used. | Computer records time of first 'interuption' section of card to pass through light beam of the light gate. Given the length of the interrupt, it can work out the trolley's initial velocity u Repeated for second interrupt to give final velocity v Computer also records time intervals t3-t1 between these two velocity measurements Formula: v-u ----- t3 -t1 |
| Explain how using ticker-timer we can measure acceleration | Tape divided into sections, every 5 dots Time interval between adjacent dots is 0.02 s. Each section represents 0.10s By placing sections of tape side by side, you can picture velocity-time graph |
| Equations of motion can only be used for: | - Motion in a straight line - Object with constant acceleration |
| What are the 4 equations of motion | 1. v= u + at 2. s=((u+v) / 2 ) x t 3. s= ut + 1/2 at^2 4. v^2 = u^2 + 2as |
| How do you use equations of motion | 1. Write quantities we know, and quantities we want to find 2. Choose equation that links quantities, substitute values 3. Calculate unknown quantities |
| Constant acceleration is referred to as | Uniform acceleration |
| How to find the acceleration of the velocity-time graph | 1. At the time of interest, mark a point on the graph. 2. Draw a tangent to the curve at that point 3. Make a large right-angled triangle, use it to find the gradient |
| What is known as the acceleration of free fall, and what is the symbol? | Measure the acceleration of a freely falling object on the surface of the earth, we find the value at about 9.81 m s^-2, and it is given by symbol g |
| Explain how we measure g using an electronic timer in the laboratory. (3) What does this tell us. (1) What equation of motion must we use to find g (1) What are sources of uncertainty (4) | A steel ball-bearing is held by an electromagnet When the current is switched off, ball begins to fall, and electronic timer starts. Ball falls through trap door and breaks circuit, stopping timer Tells us time taken for ball to fall from rest trough distance h between bottom of baal and trapdoor H=1/2gt^2 Electromagnet may retain some magnetism when it is switched off, can slow balls fall Time t recorded by timer may be longer than if ball were to fall completely freely - From h=1/2gt^2 if t is to great, experimental value of g will be too small Measuring height h is awkward and value of h will be given ±1 mm at best |
| Explain how we measure g using ticker-timer in the laboratory Where does the main problem arise | A weight falls As it falls, it pulls a tape through ticker timer Spacing of dots on tape increases steadily, showing weight is accelerating Analyse tape to find acceleration Main problem arises from friction between tape and ticker-timer. It slows down the fall of the weight so its acceleration is less than g. Friction is less of a problem if the weight is larger, thus falling more freely |
| Explain how we measure g using a light gate in the laboratory What is this methods advantage over measuring g using an electronic timer. | Weight can be attached to card 'interrupt'. Card is designed to break light beam twice as weight falls. Computer can calculate velocity of the weight twice as it falls, and hence finds its acceleration Weight can be dropped from different heights above light gate. Allows you to find whether acceleration is the same at different points in its fall. |
| A ball is bounced. Vertical motion of ball is affected by (1), that is its (2). When it rises it has the vertical deceleration of (3) which (4. slows it down/ speeds it up) and when it falls it has an acceleration of g which (5. Slows it down / speeds it up). The ball's (6) motion is unaffected by gravity. In absence of air resistance, the ball has constant velocity in (7) direction. | 1. force of gravity 2. Weight 3. magnitude g 4. Slows it down 5. speeds it up 6. Horizontal 7. Horizontal |
| For a velocity v at an angle 0 to the x-direction the components are: | X-direction: v cos 0 y-direction : v sin 0 |
| To find the components of any vector in a particular direction, we use following strategy: | 1. Find angle 0 between vector and direction of interest 2. Multiply vectors by cosine of the angle 0 |
| What is the relevant eqation of motion | V^2 = u^2 + 2as |
| One of the characteristics that make up a 'Newton's third law pair is forces of the same type. Give 5 examples of this? | 1. Gravitational forces 2. Electrical forces 3. Contact forces 4. Tension forces 5. Magnetic forces |
| One of the characteristics that make up a 'Newton's third law pair is forces of the same type. Give 5 examples of this? | 1. Gravitational forces 2. Electrical forces 3. Contact forces 4. Tension forces 5. Magnetic forces |
| What is the formula for resultant force and how is it written in symbols? | Mass x acceleration F = ma |
| What is the symbol and unit for resultant force | Symbol = F Unit = N (newtons ) |
| What is the symbol and unit for mass | Symbol = m Unit = kg (kilograms) |
| What is the symbol and unit for acceleration | Symbol = a Unit = m s^-2 (meters per second squared) |
| What is Newton's second law of motion? | For a body of constant mass, its acceleration is directly proportional to the resultant force applied to it |
| The equation a = F / m relates acceleration, resultant force and mass. What does it show in particular? | It shows that the bigger the force, the greater the acceleration it produces |
| What is inertia? | The mass of an object is a measure of its inertia, or its ability to resist any change in its motion Greater the mass, smaller the acceleration that results |
| Define the centre of gravity of an object | Centre of gravity of an object is defined as the point where its entire weight appears to act. |
| What effect does the smaller mass of the moon compared to Earth have on its gravity? | It has weaker gravity |
| What is the acceleration of freefall on the Moon? | GMoon = 1.6 m s^-2 |
| What is the symbol, unit and base unit of mass | Symbol = m Unit = kg In terms of base units = kg |
| What is the symbol, unit and base unit of weight? | Symbol = mg Unit = N In terms of base units = kg m s^-2 |
| In the 17th century Galileo came to 2 conclusions about the natural motion of objects, what are they | 1. An object at rest will stay at rest, unless a force causes it to start moving 2. A moving object will continue to move at a steady speed in a straight line, unless a force acts on it. |
| What is uniform motion? | Natural state of motion of an object |
| What is Newton's first law of motion? | If no resultant force acts on an object it will not accelerate. The object will either remain stationary or it will continue to travel at a constant velocity. |
| What is known as terminal velocity? And what is it approximately ? | Maximum velocity 120 miles per hour (about m s^-1) |
| Air resistance is just one example of (?) that objects experience when they move through a fluid, a liquid or a gas | Resistive force |
| What is contact forces? | When two objects touch each other, they exert a force on the other |
| What is Newton's third law of motion | When 2 objects interact, each exert a force on the other, forces are equal and opposite to each other |
| What are the 4 characteristics that 2 forces have that make up Newton's third law pair | 1. Act on different objects 2. Equal in magnitude 3. Opposite in direction 4. Forces of the same type |
| One of the characteristics that make up a 'Newton's third law pair is forces of the same type. Give 5 examples of this? | 1. Gravitational forces 2. Electrical forces 3. Contact forces 4. Tension forces 5. Magnetic forces |
| What are 6 examples of base units? | -meter -kilogram - Second - Ampere - Kelvin -Mole |
| What is the base unit and the symbol for length? | Symbol = x,l,s and so on Base unit = m (meter) |
| What is the base unit and symbol for mass? | Base unit = kg (kilograms) Symbol = m |
| What is the base unit and symbol for time | Base unit = s (second) Symbol = t |
| What is the base unit and symbol for electric current? | Base unit = A (Ampere) Symbol = I |
| What is the base unit and symbol for thermodynamic temperature? | Base unit = K (kelvin) Symbol = T |
| What is the base unit and symbol for amount of substance? | Base unit = mol (mole) Symbol = n |
| What is the symbol and the multiple for the prefix kilo? | Multiple = 10^3 Symbol = k |
| What is the symbol and the multiple for the prefix mega? | Symbol = M Multiple = 10^6 |
| What is the symbol and the multiple for the prefix giga? | Symbol = G Multiple = 10^9 |
| What is the symbol and the multiple for the prefix tera ? | Symbol = T Multiple = 10^12 |
| What is the symbol and the multiple for the prefix deci ? | Symbol = d multiple = 10^-1 |
| What is the symbol and multiple for the prefix centi? | Symbol = c Multiple = 10^-2 |
| What is the symbol and multiple for the prefix milli? | Symbol = m Multiple = 10^-3 |
| What is the symbol and multiple for the prefix micro? | Symbol = µ Multiple = 10^-6 |
| What is the symbol and multiple for the prefix nano? | Symbol = n Multiple = 10^-9 |
| What is the symbol and multiple for the prefix pico? | Symbol = p Multiple =10^-12 |
| Vectors have both ? | Magnitude and direction |
| When adding 2 or more forces that act in a straight line, what must we take into account? | We have to take account of their direction |
| When you draw a scale drawing you should: | 1. State the scale used 2. Draw large diagram to reduce the uncertainty |
| What are the forces that are acting on a trolley on a ramp ? | 1. Wight of the trolley (acts vertically downwards ) 2. Contact force of a ramp - acts at right angles to ramp |
| Cos(90* - θ) = | Sin θ |
| Define centre of gravity? | The point where all the weight of the object may be considered to act |
| Forces can have turning effect, what does this mean? | They can make an object turn around |
| Moments of a force depends on what 2 quantities? | 1. Magnitude of the force 2. Perpendicular distance of a force from a pivot |
| What is the formula for calculating moment of a force? | Moment of a force = force x perpendicular distance |
| What are the 2 methods to calculate the moment of the force {1(5)} {2(4)} | 1 Draw a perpendicular line from the pivot to the line of a force Find distance x`2 Calculate moment of force = F`2 x x`2 From the right angle triangle we can see that : x`2 = d sin θ Moment of force = F`2 x d sin θ = F`2 d sin θ 2 Calculate component of F`2 that is at 90° to the lever F`2 sin θ x d Moment of a force = F`2 d sinθ |
| We can use the moment of a force to solve two sorts of problems? | 1. Check whether an object will remain balanced or state to rotate 2. Calculate an unknown force or distance if we know that an object is balanced |
| What does the principle of moments state? | The principle of moments states that, for any object that is in equilibrium, the sum of the clockwise moments about any point provided by the forces acting on the objects equals the sum of the anticlockwise moments about the same point |
| Think about a car steering wheel. The 2 forces balance up and down, so the wheel does not move up down or sideways 1. Is the wheel at equilibrium 2. What will the pair of forces cause to happen? 3. What are the pair of forces known as? | 1. The wheel is not in equilibrium 2. The pair of forces will cause it to rotate 3. Couple |
| A couple has a turning effect, but does not cause an object to accelerate. To form a couple, the two forces must be:...(3) | 1. Equal in magnitude 2. Parallel but opposite in direction 3. Separate by distance d |
| What is known as torque | The turning effect or moment of a couple is known as its torque |
| The torque of a couple is known defined as follows: | Torque of a couple = one of the forces x perpendicular distance between the forces |