Question

A 60.0 kg object is moving east at 8.00 m/s, and then slows down to 4.00 m/s. How much work was done?

–1,440 J
–480 J
1,440 J
2,880 J

Answer 1

The answer is  -1440. That is letter A.

Answer 2

Work done, W = -1440 J

Step-by-step explanation:

It is given that,

Mas of an object, m = 60 kg

Initial velocity of the object, u = 8 m/s

Final velocity of an object, v = 4 m/s

We know that work done is equal to change in kinetic energy of an object as per work energy theorem.

`W=(1)/(2)mv^2-(1)/(2)mu^2`

`W=(1)/(2)m(v^2-u^2)`

Putting all the values in above equation we get :

`W=(1)/(2)* 60\ kg((4\ m/s)^2-(8\ m/s)^2)`

W = -1440 J

So, the work done by the object is -1440 Joules. Hence, the correct option is (A) " -1440 J ".