| To find out how long it will take form leaving your hand for the stone to fall back to the clifftop. What equation do we use to substitute the values into? | s= ut + 1/2 at^2 |
| To find out how long it will take form leaving your hand for the stone to fall back to the clifftop. What equation do we use to substitute the values into? | s= ut + 1/2 at^2 |
| To find out how long it will take form leaving your hand for the stone to fall back to the clifftop. What equation do we use to substitute the values into? | s= ut + 1/2 at^2 |
| 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. A negative slope shows | Deceleration |
| 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 |
| To find out how long it will take form leaving your hand for the stone to fall back to the clifftop. What equation do we use to substitute the values into? | s= ut + 1/2 at^2 |
