Question

A knife of mass m is at a height x from a large wooden
block. The knife is allowed to fall freely, strikes the
block and comes to rest after penetrating distance y.
The work done by the wooden block to stop the knife is
(1) mgx
(2) -mgy
(3) - mg (x+y)
(4) mg (x - y)​

Answer 1

Answer:

3 rd option

Explanation:

work = force × displacement

force=gravity ( mg)

disp = x+ y

force is exerted in the opposite direction of motion so work done is negative

hence

W= - mg ( x+ y)