Starter quiz
- A student measures the time taken for a toy parachute to fall from a particular height. She repeats the measurement and gets these results: 1.60 s, 1.53 s, 1.52 s. The mean time taken is ______ s.
- '1.55' ✓
- A toy car travels at a constant velocity along a straight track. It travels 90 cm in 20 s. The velocity of the toy car is ______ m/s along the track.
- '0.045' ✓
- A car accelerates steadily from rest to 20 m/s in a time 8.0 s. The acceleration of the car is ______ m/s.
- '2.5' ✓
- A student measures the acceleration of a trolley along a slope for different values of the force pulling the trolley. Which of these is the independent variable in this experiment?
- the angle of the slope
- the mass of the trolley
- the acceleration of the trolley
- the force acting on the trolley ✓
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- A trolley travels down a slope. It is stationary at the start and gets faster as it moves. A student takes measurements and calculates: (distance travelled) ÷ (time taken). What has the student found?
- the speed at the start
- the speed at the end
- the average speed ✓
- the acceleration
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A trolley is stationary at position A and then accelerates along the track. A student wants to measure the trolley’s average acceleration between A and C. Which of these calculations should be used?- (average speed between A and D) ÷ (time from A to C)
- (average speed between A and D) ÷ (time from A to D)
- (average speed between B and D) ÷ (time from A to C) ✓
- (average speed between B and D) ÷ (time from A to D)
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Exit quiz
- A ______ is an instrument that uses an infrared beam to turn a timer on and off as an object passes through.
- 'light gate' ✓
- A trolley takes 3.50 s to travel along a ramp. Its starting velocity is 0 and its final velocity is 0.42 m/s. The acceleration of the trolley is ______ m/s.
- '0.12' ✓
A student wants to find the relationship between force and acceleration of a trolley. He will use masses on a hanger to pull the trolley. To make the test fair, how should he increase the force?- by putting more masses onto the trolley
- by putting more masses onto the hanger
- by moving masses from the trolley to the hanger ✓
- by moving masses from the hanger to the trolley
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The picture shows a trolley with three 100 g masses resting on it, and two 100 g masses attached to the trolley by a string. If friction can be ignored, what is the accelerating force on the trolley?- 1 N
- 2 N ✓
- 3 N
- 5 N
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- A student wants to find the relationship between force and acceleration of a trolley on a track. Before taking measurements, she tilts the track at an angle. The reason for this is to make sure that …
- the accelerating force is caused only by the hanging masses. ✓
- friction and drag make the trolley accelerate.
- gravitational force makes the trolley move down the track.
- the trolley moves down the track even when no masses are attached to it.
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- If two variables, and , are directly proportional, which of these statements are correct?
- If halves, halves. ✓
- If increases by 2, increases by 2.
- A graph of against is a straight line. ✓
- A graph of against passes through the origin. ✓
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Worksheet
Presentation
Video
Lesson Details
Key learning points
- A dynamics trolley has a steady acceleration down a steep ramp.
- Acceleration = change of velocity ÷ time and change in velocity = final velocity – initial velocity
- Light gates can improve accuracy of measurement of instantaneous velocity and reduces random errors.
- For a fair test, total mass of the system must be kept constant.
- A compensated ramp can counteract the effect of friction.
Common misconception
Pupils may compare the accelerations of objects on the basis of final velocities and may fail to take into account the time interval over which the change in velocity occurred.
Provide pupils with opportunity to analyse measurements of changes in velocity in which the starting velocities vary. A pair of light gates at two positions along the ramp will allow this.
Keywords
Compensated ramp - A ramp with a slope to counteract the effect of friction.
Final velocity - The final velocity of an object is the velocity it finishes with after a phase of motion.
Light gate - A light gate can be used to measure velocity. It uses an infrared beam to turn a timer on and off as an object passes through.
Repeatable - Measurements are repeatable if they are very similar when the same procedure is carried out by the same person or team.
Uniform acceleration - When the acceleration is constant, it is described as uniform acceleration.