Question

A man is pushing the box up along an inclined plane as shown. Its free body diagram will be:

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

Following are the forces which will act on the block:
1. Gravitational force ( <!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> $F_G$), due to its own weight, will act vertically downwards.

2. Normal force ( <!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> $F_N$) will always act perpendicular to the surface on which the object is kept. Here the normal force will act perpendicular to the inclined plane.

3. Force applied by the man ( <!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> $F_{applied}$) will act up along the inclined plane.

4. Frictional force ( <!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> $F_f$) will always try to oppose the relative motion of the block. In the given case since the man is pushing the block up along the inclined plane, frictional force will act down the inclined plane.

So, the FBD (Free Body Diagram) of the block will be: