Science Class 9
Work, Energy, and Simple Machines
When a push does work, stored energy, work from a graph, and what machines trade.
14 lessons · ~87 min total
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Lessons in this topic
- 0 Start here What work, energy and power mean in science, and how machines help. · 3 min You are here
- 1 When a push does work Work is force times the distance moved along the force. · 6 min
- 2 Two kinds of energy Kinetic energy is ½mv². Potential energy near the ground is mgh. · 6 min
- 3 Energy changes form Energy changes form but is never created or destroyed. · 7 min
- 4 Where it seems to vanish Friction turns mechanical energy mostly into heat. The total energy is not lost. · 6 min
- 5 Power Power is work divided by time. Its unit is the watt. · 6 min
- 6 A machine trades force for distance A machine changes the force you need, not the work. Advantage is load over effort. · 7 min
- 7 Three machines A fixed pulley turns the force round. A lever balances arm times force. A ramp is length over height. · 7 min
- 8 Nothing is free No machine gives out more work than it takes in. Friction turns some into heat. · 6 min
- 9 Energy stored in a stretch A stretched or squeezed springy object stores potential energy. · 7 min
- 10 Work from a graph Work is the area under a force–displacement graph. · 8 min
- 11 Checkpoint: stored energy and graphs A graded check on the last two lessons. · 6 min
- 12 The big picture Work, energy, power, graphs and machines, on one screen. · 4 min
- 13 Track quiz The ten rules, then one question on each idea. · 8 min
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