Acceleration - Newton's second law
Investigate how varying force (at constant mass) or varying mass (at constant force) affects acceleration.
Check your understanding with these quick common questions. Use the drop down boxes to see the correct answers.
Forces & Acceleration
Acceleration is effected by the force on an object and the mass of the object. This practical investigates either the effects of force on the trolley or the mass. Its hard to measure the force if you push by hand, so the trolley is pulled with a string and a pulley and dropping weights.
Independent variable: Either force (via hanging mass) or mass of trolley.
Dependent variable: Acceleration (from light-gate timing).
Control variables (3): Track angle (friction), same trolley/wheels; same timing method. Same distance from light gate to trolley.
Light gate to measure acceleration
Data logger
Trolley and track/ramp
Weights
Accuracy can be improved by: Ensure the trolley goes through the light gate BEFORE the weights hit the ground so it is still accelerating
Use a light gate and data logger so calculations are automatic and there is no reaction time error.
Validity- Can be improved by reducing the effects of friction - use an air track or have the trolley on a slight slope.
Other improvements: Repeat and calculate a mean.
The total mass of the system should be the same. So masses should be moved from the trolely and added to the falling stack.
The graph should show a directly proportional relationship.
Plot acceleration on the y axis
Change the force on the trolley by attaching weights to a string and connecting to the trolley with a pulley.
Use 5 different weights, e.g. 1N, 2N - 5N.
Place a 1kg stack of masses onto the trolley.
Measure the acceleration using the formula acceleration = change in speed / time taken.
Set up a light gate and data logger to do this automatically.
Ensure the mass of the system stays the same by moving the masses from the trolley to the end of the string.
Release the trolley - do not add extra force.
Control the distance from the start line to the light gate.
Repeat 3 times for each weight and calculate a mean.