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A 61kW crane lifts a 1.0 ton (1000kg) mass up a height of 15.0m in 10.0s. What is the efficiency of the crane? (24%)

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Presentation on theme: "A 61kW crane lifts a 1.0 ton (1000kg) mass up a height of 15.0m in 10.0s. What is the efficiency of the crane? (24%)"— Presentation transcript:

1 A 61kW crane lifts a 1.0 ton (1000kg) mass up a height of 15.0m in 10.0s. What is the efficiency of the crane? (24%)

2 A 30 kg box is pushed along a rough surface at a constant speed of 2
A 30 kg box is pushed along a rough surface at a constant speed of 2.3 m/s against a friction force of 78 N a) Find the work done by the pushing force in 1.0 minutes (11000J) b) Find the amount of heat dissipated by the frictional force in 2.0 minutes. (22000J)

3 A rollercoaster car with total mass 322 kg has a velocity of 12 m/s at a height of 17 m. It rides a perfectly frictionless track and is amazingly streamlined so air resistance is negligible. a) Find its velocity at a height of 13 m (15m/s) b) Find the height at which the velocity is 2.5 m/s (24m) c) It starts from rest at its highest point. Find the height of this point. (24.3m -> 24m) d) How much work was done to lift the car to its maximum height? (77000J)

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