MEDAL GIVEN TO CORRECT ANSWERS.
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?

A. -784 J
B. -80 J
C. 784 J
D. 80 J

Question

MEDAL GIVEN TO CORRECT ANSWERS. 
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?

 		A.	-784 J
 		B.	-80 J
 		C.	784 J
 		D.	80 J

anonymous · Answer

Letter C, Work is given by Force times distance, now, weight is a force, and F=ma , mass being 40kg, and acceleration is the gravity $$9.81 m/s ^{2}$$ then the force applied by the block's weight is 40x9.81= 392.4 N, Then W=392.4 N x 2m, W= 784.8 J