 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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