Specified practical

Determination of the acceleration of a moving object

An object moving down an inclined ramp will accelerate. If the object starts from rest at the top of the ramp, the velocity of the object at the bottom of the ramp can be used to calculate the mean acceleration of the object, using the equation:

  • acceleration = \frac{change\ in\ velocity}{time\ taken}

or

  • acceleration = \frac{velocity\ at\ bottom\ of\ ramp}{time\ taken}

The velocity at the bottom of the ramp can be calculated from the time the object takes to move a measured distance along the bench.

A squash ball Is at the top of a slanted runway. A clamp on a stand holds the runway in place and there is a 50cm flat surface at the end of the runway.A squash ball is at the top of a slanted runway. A clamp on a stand holds the runway in place and there is a 50 cm flat surface at the end of the runway

Aim of the experiment

To investigate the effect of varying the force on the acceleration of an object.

Method

  1. Use the stand and clamp to set the height of the top end of the runway 10 cm above the table.
  2. Measure and mark a distance of, eg 50 cm, from the bottom of the runway along the table.
  3. Release the ball from the top of the runway at the same time as starting the stopwatch.
  4. When the ball reaches the bottom of the runway, press the 'split' or 'lap' button on the stopwatch.
  5. Stop the stopwatch when the ball reaches the 50 cm mark.
  6. Record the time for the ball to travel down the runway and the total time of the journey.
  7. Repeat steps 1 - 6, increasing the height in 5 cm intervals up to 30 cm.
  8. Repeat the experiment twice again to give 3 sets of results.

Results

It is important to record results in a suitable table, like the ones below:

Time to reach bottom of runway in seconds

Height above table in cmTrial 1Trial 2Trial 3Mean time
10
15
20
25
30

Time to travel 50 cm along table in seconds

Height above table in cmTrial 1Trial 2Trial 3Mean time
10
15
20
25
30

Velocity and acceleration

Height above table in cmVelocity at bottom of runway (m/s)Acceleration when moving down the track (m/s²)
10
15
20
25
30

Analysis

  1. Calculate the time taken for the ball to travel 50 cm along the table. (Total time − split/lap time).
  2. Calculate the velocity at the bottom of the runway using the equation: velocity = 0.5 ÷ mean time taken to travel 50 cm along the bench.
  3. Calculate the acceleration using the equation: acceleration = velocity at bottom of runway ÷ mean time to reach bottom of runway.
  4. Plot a graph of runway height against acceleration.

Describe what the results show about the effect of increasing the height on the acceleration of the object.

Evaluation

Acceleration is directly proportional to the height of the object. It is important to consider to what extent the results show this relationship. For example, do all the points lie on a straight line passing through the origin, or are there any anomalous points?

Hazards and control measures

HazardRiskControl Measures
There is no significant risk in carrying out this experiment.