1. Ticker timer (how to use a ticker timer to measure “g”)

2. Ticker timer: A ticker timer is an equipment which can measure distance, speed and acceleration. coil magnet ticker tape power input (a.c.) vibrating bar carbon paper disc

3. How to make an experiment: What we need: Ticker-timer with power supply unit Ticker-tape Ball breaker Ruler & Pencil Preparation: To make the ticker-timer on the edge to the table To make the ticker-tape in the ticker-timer fixed with a clamp To make one end of the ticker-tape, which is closed to the ticker-timer, connected with a ball breaker To make a connection with the clamp and the ball breaker

4. Steps : ·Open the power, see whether the ticker-timer is working ·Open the clamp and let the ball breaker itself do the free fall ·We can get a constant points on the ticker-tape ·Use the ruler to measure the distance between the first three points as S1(since the first clear point from the eyes), and the distance of the three points in the middle as S2

5. ·We know that v=S/t, and we get that v1=S1/2t, v2=S2/2t (t=0.02s) ·We get v1 and v2, and we can point out the number of the points between v1 and v2, suppose it is n, so the acceleration of the gravity is: g=(v2-v1)/(n+1)t ·Continue the steps again and again, with different weight of ball breakers, and calculate the value of “g”, get the average of it

6. It’s reliable in some ways, for there is a chain wheel between the ball breaker and the clamp, it can reduce the resistance of the ticker-tape. In addition, because the weight of the ball breaker is heavy enough, we can nearly ignore the air resistance of the substance. Reliable??!!

7. Errors: Systemic errors: The points made by the ticker-timer is not always clear The scale of a ruler is sometimes unreliable Random errors: There is an resistance between the ticker-tape and the chain wheel We may measure a little different with the true value of the distance between the points

8. Addition: Actually, there is another way to measure “g” with the ticker-timer. Just make the ticker-timer and the ticker-tape in a vertical direction. Thus we can reduce the resistance between the chain wheel and the ticker-tape. Remember, we must open the power of the ticker-timer firstly. There is also a picture for us to understand the experiment.

9. That's all, thank you!