Question

A dart is loaded into a compressed spring. Starting from rest the spring is released and shoots the dart up into the air. From the instant the dart is released (before it starts to move) until it reaches its maximum height, what is the Net work done on the dart

Answer 1

Wnet = 0

Step-by-step explanation:

• The work-energy theorem says that the total net work done on an object, is equal to the change in the kinetic energy of that object.
• In this case, the total change in kinetic energy of the dart is zero, due to the initial status is at rest (loaded into a compressed spring) and the final is also at rest (when it reaches to its maximum height).
• The total work done on the dart can be written as follows:

`W_(net) = (1)/(2) k* \Delta x^(2) - m*g*h_(max) (1)`

• Now, in absence of friction, all the elastic potential energy becomes gravitational potential energy, so the following is true:

`(1)/(2) k* \Delta x^(2) = m*g*h_(max) (2)`

• From (1) and (2) we conclude that Wnet = 0.