Physics P4 Explaining motion

1. Energy is a moving object called kinetic energy

2. As an object falls its gravitational potential energy decreases

3. when a force causes movement work is done

4. Work done by force = force x distance moved in the direction of the force

              joule J            newton N                          metre M

5. Change in energy = work done

6. Change in GPE= weight x vertical height difference

            joule J              newton N               metre M

7. The heavier and faster an object is moving changes its kinetic energy

8. Kinetic energy = 1/2 x mass x Velocity squared

             joules J            kilogram kg       metre per second m/s squared

9. excluding air resistance, a object's kenetic energy will equal the work done to it.

1. When a object is pushed forces are present

2. The resultant force on a object is determined by all of the forces acting on it.

3. Momentum = mass x velocity

            kg m/s        kg        m/s

4. change of momentum = resultant force x time for which it has it act

                         kg m/s                 N                                S

5. Cars and bicycles have a driving force and a counter force (air resistance)

6. If the driving force is larger than the counter force the vehicle will speed up

7. If the counter force is larger the vehicle will slow down

1. Forces arise from the interaction between two objects

2. Friction from the road serface affects the forces

3. Rockets and Jet engines use forces to propel them

1. Speed = Distance divided by Time taken

         m/s            M                             S

2.  Average speed is an average over a short interval

3. Instantaneous speed is Instantaneous 

4. When a line is horizontal on a distance/time graph it means that there is no motion taking place