Potential and kinetic energy on a ramp
Release a trolley from different heights on smooth and rough ramps and watch its potential energy turn into kinetic energy.
Core concept
Gravitational potential energy (mgh) turns into kinetic energy (½mv²); some becomes heat when there is friction
Topic: Work, energy and power
An object raised above the ground has gravitational potential energy: What is needed to make things move, heat up, light up or grow. All key words: PE = m × g × h. When it rolls down a ramp, this energy changes into kinetic energy, the energy of movement: KE = ½ × m × v². Energy is never created or destroyed, only changed from one form to another. On a smooth ramp almost all the potential energy becomes kinetic energy. On a rough ramp friction: A force that slows things down when two surfaces rub together. All key words changes some of it into heat, so the trolley reaches the bottom more slowly.
What you will learn
- Calculate gravitational potential energy using PE = mgh.
- Use the conservation of energy to find the speed at the bottom of a ramp.
- Explain where the 'missing' energy goes on a rough ramp.
Before you start
- Know that energy is measured in joules (J).
- Know that weight = mass × g.
Materials
- Trolleys of 0.5 kg, 1 kg and 2 kg
Equipment
- Ramp that can be set at different heights
- Light gate or stopwatch to measure speed
- Metre rule
Procedure
- Release the 1 kg trolley from three different heights on the smooth ramp and record each run.
- Release a 2 kg trolley from the same height as one of your runs and compare the speed.
- Change to the rough ramp, release the trolley again and see where the energy goes.
How this simulation is simplified
- g is taken as 10 N/kg.
- The smooth ramp has no friction or air resistance; the rough ramp turns a fixed 25% of the energy into heat.