Work done in a system is ___
a) The measure of energy change
b) The measure of useful work
c) The measure of displacement
d) The measure of force

Answer

A, B

Explanation

The driving force on the block whch makes the body to move down the plane is,
`F=mg sin theta `
` :. Acceleration = g sin theta`
Initial velocity of block, u=0
S=l
`a= g sin theta `
Now, ` S= ut+1/2at^2`
`rarr l=0+1/2(g sin theta)t^2`
` rarr t^2 = (2l)/(g sin theta)`
` rarr Time taken, `t= (2l)/(g sin theta`.