The method and the results are on the newton's laws lab. Do the analysis yourself first, then check the answers below.
Quick answer: Newton's first law says an object keeps its motion unless an unbalanced force acts on it. These answers go with the grade 8 science lab on newton's laws: the graph, the calculations, the uncertainties and the conclusion explained, for all 7 analysis questions.
Model answers use the sample table. Your own times will differ, but the product of total mass and acceleration should stay roughly constant and a little below the weight of the hanger because of friction.
0.60 × 1.44 = 0.86; 1.10 × 0.80 = 0.88; 1.60 × 0.54 = 0.86; 2.10 × 0.41 = 0.86. The product is about 0.86 N each time, so the acceleration is inversely proportional to the mass.
Question 3 Graph
The graph is a falling curve: acceleration decreases as mass increases. Plotting acceleration against 1 ÷ mass gives a straight line through the origin whose gradient is the force.
Question 4 Compare with the weight
Difference = 0.98 − 0.86 = 0.12 N. 0.12 ÷ 0.98 × 100 = 12 %. The missing force is the friction in the wheels and pulley, which opposes the pull.
Question 5 Control variables
Independent: total mass moving. Dependent: acceleration (from the time). Keep the same pulling force (hanger mass), the same distance and the same starting position.
Question 6 Timing uncertainty
Time: 0.1 ÷ 1.18 = 8.5 %. Because a depends on t², the percentage uncertainty doubles: about 17 %.
Question 7 Improvements
Use light gates or video analysis to time the motion, and tilt the runway slightly so gravity cancels friction. Any two sensible improvements earn full credit.
