The trolley practical that tests F = ma: variables, light gates, ticker tape or video, a results table, the graph of acceleration against force, and a full method.
What you will learn
- Name the variables when force or mass is changed
- Work out an acceleration from light gate, ticker tape or video readings
- Process a results table and read the gradient and intercept of a graph of a against F
- Write a 6-mark method with its hazards
What you are finding out
A trolley on a runway is pulled by a string that runs over a pulley to a hanger of slotted masses.
The weight of the hanging masses is the force that accelerates everything. There are two versions.
- Changing the force: move masses one at a time from the trolley to the hanger. The force goes up, but the total mass being accelerated stays the same, so it is a fair test.
- Changing the mass: add masses to the trolley and keep the same hanging mass, so the force stays the same.
- investigation: how does acceleration depend on force?
- independent: the weight of the hanging masses
- dependent: the acceleration of the trolley
- control: the total mass, the runway, its slope and the start position
Before you start, tilt the runway a little until a gently pushed trolley keeps a steady speed. Its weight down the slope then balances friction.
The rest of this lesson and its 11 practice questions are locked.
In this lesson
- What you are finding out
- Measuring the acceleration
- The results table and the graph
- Writing the method
- Try it: Why each step?
11 practice questions, marked as you go; about 25 minutes in all.
Key terms
Total mass, Acceleration against force
In this unit: Forces and motion
Speed, velocity and acceleration, the graphs that show them, the equations of motion, Newton's laws and stopping distances.
- Speed, distance and velocity
- Distance-time graphs
- Acceleration and velocity-time graphs
- The equations of motion
- Newton's laws
- Stopping distances
- Required practical: force, mass and acceleration