Question

Point A is on the ground, and points B and C are h = 20 meters above the ground. Point B is directly above point A, and point C is L = 40 meters away from point A as shown.(a) How much work must be done by an external agent to move a 2 kg object from rest at point A to rest at point B?(b) How much work must be done to move the same object from rest at point A to rest at point C?

Answer 1

Given the mass of the object, m = 2 kg

Distance between point A and B, h= 20 m

(a) To find work done in moving the object from A to B

Work done is

`\begin{gathered} W1=Force* displacement\text{ } \\ =mgh \end{gathered}`

Here, g is the acceleration due to gravity whose value is 9.8 m/s^2.

Substituting the values, we get

`\begin{gathered} W1=2*9.8*20 \\ =\text{ 392 J} \end{gathered}`

(b) To find work done in moving the object from A to C

Gravitational force is a conservative force and work done depends only on the initial and final position and not on the path.

So, the work done will be

`\begin{gathered} W2=\text{mgh} \\ =2*9.8*20 \\ =\text{ 392 J} \end{gathered}`