P2.2.1- Forces and Energy

P2.2.1- Forces and Energy

1. When a force causes an object to move through a distance, work is done

   • Work Done (J) = Force (N) x Distance (m)
     • Work Done = Energy Transferred

2. Space Shuttle Re- entering Earth's Atmosphere

   • When a space shuttle returns to Earth, it has a lot of Kinetic Energy because it has a large mass and a high velocity
     • The Shuttle encounters enormous frictional forces which cause it to decelerate. Some of the KE is converted to heat, which means the shuttle is subjected to extremely high temperatures

3. Meteorites entering Earths Atmosphere

   • They have large amounts of KE because they travel at a very high speed when they enter the Earth's atmosphere
     • As it travels into the atmosphere, it encounters a lot of air resistance. This causes it to decelerate, lose KE and heat up. As the outer layers get hotter, the meteorite loses energy to the surroundings air in the form of heat and light
       • As it continues its journey, the surface layers become so hot that VAPOURISATION BEGINS. Continued heating causes more and more surface mass to be lost and in most cases, the meteorite is completely vapourised before reaching planets surface

4. Work is done against frictional forces

5. Power is the work done or energy transferred in a given time

   • Power (W) = Energy Transferred (J) / Time (s)

6. GPE is the energy that an object has by virtue of its position in the gravitational field

   • GPE (J) = Mass (kg) x (gravitational field strength (N/kg) x Height (m)
   • When an object is raised through vertically, work is done against the gravitational force and the object gains GPE

7. The Kinetic Energy of an object depends on its mass and speed

   • KE (J) = 0.5 x Mass (kg) x Velocity^2 (m/s)