The method and the results are on the speed and velocity lab. Do the analysis yourself first, then check the answers below.
Quick answer: Speed is distance divided by time, while velocity is displacement divided by time and includes direction. These answers go with the Physics 9-10 lab on speed and velocity: the graph, the calculations, the uncertainties and the conclusion explained, for all 7 analysis questions.
The model answers use the sample table. Your own times will differ a little, but the average speed should rise with distance and the acceleration should be roughly constant for your slope.
Level: Physics grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: IGCSE 1.2, HS-PS2-1
Question 1 Average speed for each distance
0.20 ÷ 0.90 = 0.222 m/s; 0.40 ÷ 1.27 = 0.315 m/s; 0.60 ÷ 1.55 = 0.387 m/s; 0.80 ÷ 1.79 = 0.447 m/s; 1.00 ÷ 2.01 = 0.498 m/s.
Question 2 Pattern in the speeds
The average speed increases with distance. If the speed were constant the average would be the same for every distance, so the ball must be speeding up, which means it accelerates.
Question 3 Final speed
v = 2 × 0.498 = 0.996, so the final speed is 1.0 m/s (2 s.f.).
Question 4 Acceleration
a = (v − u) ÷ t = (1.0 − 0) ÷ 2.01 = 0.4975, so 0.50 m/s².
Question 5 Repeat readings
Mean = (2.00 + 2.03 + 1.99) ÷ 3 = 6.02 ÷ 3 = 2.01 s. Uncertainty = (2.03 − 1.99) ÷ 2 = 0.02 s. Percentage = 0.02 ÷ 2.01 × 100 = 1.0 %.
Question 6 Sources of error
Human reaction time of about 0.2 s is large compared with the short times for the first marks, and it varies from run to run. Better: use two light gates linked to a data logger, or film the run in slow motion on a phone and count frames.
Question 7 Converting the result
1.0 m/s × 3.6 = 3.6 km/h, about the speed of a slow walk. That is reasonable for a ball on a gentle slope 1 m long.
