A box is sliding on a rough surface at a constant speed. Which statement is TRUE?...

A box is sliding on a rough surface at a constant speed. Which statement is TRUE?

1. Work done by gravity is negative

2. Friction deos not do any work

3. Work done by friction is negative

4 Work done by friction can be either positive or negative depending on direction of motion?

Expert Solution

The right option for this Question is [4] Work Done by Friction is Negative.

When a body slides along a surface (horizontal) then the Work Done by Gravity is Zero, Which rules out option number 1.

Since the Body is sliding along a Rough surface Friction does work, which rules out Option 2.

As for option 4 , it is a little tricky. Friction can do positive work in reference to another frame. For example, If you have two block arranged on top of each other and they start acclerating , then the work done by friction on the top body is going to be positive with respect to the bottom body. So Work Done by friction is Going to be a relative tearm here, which rules out option 4 as we are considering a single frame with one moving body.

This leaves us with option 3 . As we all know friction is an opposing force, the work done by friction on the moving object is going to be negative.

Hope this Helps!!

genius_generous answered 1 year ago

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