Question

You hold a metal block of mass 40 kg above your head at a height of 2 m.

How much work is done by gravity if you let the block fall to the ground?
O A. -80 j
O B. 80
O C. 784 J
O D. -784

Answer 1

C. 784 J

Step-by-step explanation:

Just got it right :)

Answer 2

The work done by gravity is 784 J.

Step-by-step explanation:

Given:

Mass of the block is,
`m=40\ kg`

Height to which it is raised is,
`h=2\ m`

Acceleration due to gravity is,
`g=9.8\ m/s^2`

Now, work done by gravity is equal to the product of force of gravity and the distance moved in the direction of gravity. So,

`\textrm{Work by gravity}=F_g* h`

Force of gravity is given as the product of mass and acceleration due to gravity.

`\therefore F_g=mg=40* 9.8=392\ N`. Now,

`\textrm{Work by gravity}=F_g* h=392* 2=784\ J`

Therefore, the work done by gravity is 784 J.