# To show that acceleration is proportional to force

When a free running trolley accelerates as a result of a force applied to it the acceleration is proportional to the applied force. In this experiment the overall mass of the system is kept constant but masses are moved from the trolley to the end of a string which is hanging over a free moving pulley. As the number of "weights" attached to the end of the string increases (the accelerating force), the acceleration increases. We will investigate the relationship between acceleration and accelerating force. A ticker timer is used to measure the acceleration.
Note: In this simulation the trolley is running on a level track. In the lab a level air track can be used or a simple runway which is tilted sufficiently to overcome friction in the wheels of the trolley and in the pulley. The mass of the trolley is 1.2 kg and the masses are 200 g each.

Procedure:
1. Press "Release Trolley".

2. Press "Get Tape and Ruler".

3. Measure a 5 dot interval near the start of the tape. This distance was travelled in 5/50 of a second. Calculate u, the initial velocity. u = distance / 0.1 m/s

4. Measure and record a 5 dot interval near the end of the tape and calculate v.

5. Count the number of dots from the start of the first interval to the start of the second. Time is given by: t = no. of dots / 50

6. Calculate the acceleration using the formula a = (v - u) / t

7. Press "Reset" and "Move Mass" to transfer a mass from the trolley to the string and repeat steps 1 to 6.

8. To completely restart the experiment press "Full Reset".

Precautions:

• Ensure that the runway in smooth, free of dust, and does not sag in the middle
• Ignore the first few dots on the tape. These are unreliable and too close together for accurate measurement.
• Place a ruler right on top of the tape with eye directly above when measuring distances to avoid parallax errors

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