Classical Mechanics

# Work done by a constant force

What is the minimum amount of work in Joules that a 60 kg man must do in order to climb up a tree house that is 3 meters high?

Details and assumptions

• The acceleration of gravity is $$-9.8\text{ m/s}^2.$$

A man who is standing on a ladder vertically lifts a book of mass $$3\text{ kg}$$ with a rope at a constant speed. If the change in the book's height is $$7\text{ m},$$ how much work did the man do on the book?

The gravitational acceleration is $$10\text{ m/s}^2.$$

A weight lifter is bench-pressing a barbell whose weight is $$650\text{ N}.$$ He raises the barbell vertically by $$0.60\text{ m}$$ above his chest with a constant velocity. How much work did the weight lifter do on the barbell?

A box with mass $$100\text{ kg}$$ is on the flatbed of a truck which is moving with an acceleration of $$a=1.5\text{m/s}^2$$ along the positive $$x$$-axis. The box does not slip with respect to the truck. If the displacement of the truck is $$s=35\text{ m},$$ what is the total work done on the box by all of the forces acting on it?

A man is pulling a sled on an icy road. The total mass of the sled is $$50.0\text{ kg},$$ and the man exerts a force of magnitude $$1.20 \times 10^2\text{ N}$$ on the sled by pulling on a rope. At a distance of $$13.5\text{ m}$$ from the starting point, the man releases the rope, and the sled stops at a distance of $$18.2\text{ m}$$ from the starting point. If the friction force between the ice and the sled is $$45.0\text{ N},$$ how much work did the friction force do on the sled?

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