Question

A plank of wood is used to help lift a heavy box of weight 500 N into the back of a truck as shown in the figure below The plank is 10 m long and the object rises a vertical height of 2m. A force of 200 N is used to pull the object along the plank.(a) Determine the change in gravitational potential energy ofthe box as it is lifted into the truck.(b) How much work is done by the 200 N force?

Answer 1

Given:

The weight of the truck is W = 500 N

The height is h = 2 m

The force applied is 200 N

To find

(a) The change in gravitational potential energy of the box when lifted into the truck.

(b) Work done when force is 200 N

Explanation:

(a) Initially, the box is at height h = 0 m

The final height of the box is h' = 2 m

The change in gravitational potential energy can be calculated by the formula

$\Delta G.P.E\text{ =Wh'-Wh}$

On substituting the values, the change in gravitational potential energy will be

$\begin{gathered} \Delta G.P.E.=\text{ 500}\times2-500\times0 \\ =1000\text{ J} \end{gathered}$

(b) The work done will be

$\begin{gathered} W=Force\times displacement \\ =200\times2 \\ =400\text{ J} \end{gathered}$