Forces and Energy

Forces and Energy

1. Work

   • Work is done whenever a force moves something
     • Both work and force are measured in J
     • Work Done is calculated as : W = F × d
       • Where W is work done in joules, F is force in Newtons and d is distance moved in m

2. Power is a measure of how quickly work is being done which basically means how fast energy is being transferred

   • Power is calculated as: P = E ÷ t
     • Where P is power in watts, E is work done in joules and t is time in seconds

3. Gravitational potential energy

   • Gravity acts on us and when we are above ground we have potential energy
     • This is called gravitational potential energy
       • Change in GPE can be calculated as: Ep = m × g × h
         • Where Ep is the chang in GPE in Joules, m is the mass in kg, g is the gravitational field strength in N/Kg ( on earth this 10 N/kg and on the moon it is 1.6 N/kg) and h is the change in height

4. Kinetic Energy

   • Kinetic energy is dependent on Mass and Speed
     • It can be calculated as: Ek = ½ × m × v2
       • Where Ek is kinetic energy in joules, m is mass in kilograms and v is speed in metres per second

5. Momentum

   • Every moving object has momentum which is a tendency to keep moving in the same direction
     • It is hard to stop or change the direction of an object with a lot of momentum
       • Momentum can be calculated as: p = m × v
         • P is the momentum in kilogram metres per second, m is the mass in kilograms and v is velocity in m/s
           • Momentum does not just depend on the object's mass and speed because velocity has direction so momentum also depends on direction
             • This means that the momentum of an object can change if the object speeds up, slows down or changes direction
   • Conservation of momentum
     • As long as no external forces are acting on the objects involved, the total momentum stays the same in explosions and collisions
       • This means momentum is conserved