- #1

yttuncel

- 28

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**Energy and Work Concept. Confusing. Help please :)**

**1. Homework Statement**

A train composed of flat cars, travels with s constant speed V along a straight

track. A crate of mass m is attached to a rope and is slowly lowered from a

bridge when the train passes under it. At the instant that the crate touches the

train, the rope is released. the create then slides some distance along the train

and after some time T, comes to rest relative to it. In answering the following

questions, describe all quantities relative to the reference frame of the bridge,

a) Is the work done on the crate, by the force due the train, positive, negative

or zero?

b) Is the work done on the train, by the force due to the crate, positive,

negative or zero?

c) Is the magnitude of the work done on the crate, by the force due to the

train, larger than, smaller than, or equal to the magnitude of the work done

on the train by the force due to the crate? Explain your answer.

d) What is the distance, which the crate slides, relative to the train before

coming to rest relative to it?

e) During the time T, what is the work on done on crate by the train?

f) During the time T, what is the work done on the train by the crate?

g) What is the coefficient of kinetic friction between the crate and the train

## Homework Equations

Nothing else than energy and work equations. No momentum is allowed yet unfortunately.

## The Attempt at a Solution

I got really confused while deciding the direction of the forces, whether both forces are friction forces or not. I need help as this is a concept question and will improve my thinking. Thanks