A box is to be moved across a level surface.A force of magnitude 200 N may be applied at an angle of 30 $\degree$below the horizontal to push the box or at an angle of 30 $\degree$above the horizontal to pull the box,either application sufficient to overcome friction and move the box.Which application will cause the box to have the greater acceleration?
A)the one below the horizontal
B)the one above the horizontal
C)both give equal acceleration
D)more information is needed

Question

Quizplus · Accepted Answer

The force above the horizontal will have a greater component in the direction of motion than the force below the horizontal. This can be seen as follows:
For the force above the horizontal, the component in the direction of motion is given by:
Fcos30° = 200cos30° = 173.2 N
For the force below the horizontal, the component in the direction of motion is given by:
Fcos(180°-30°) = Fcos150° = 200cos150° = -173.2 N (since cos150° = -cos30°)
Therefore, the force above the horizontal will cause the box to have a greater acceleration.

A Box Is to Be Moved Across a Level Surface °\degree°

A Box Is to Be Moved Across a Level Surface $\degree$