A block of mass 1kg is free to move along the X-axis. It is at rest and from time t=0 onwards it is subjected to a time-dependent force F(t) in the x-direction. The force F(t) varies with t as shown in figure. The kinetic energy of the block at t=4s is

Options

A. 1J
B. 2J
C. 3J
D. 0J

Answer

D

Explanation

`because` Total mementum of block= Area of given graph
`therefore P= A_(1) +A_(2) + A_(3)`
or `P= (1)/(2) xx 1 xx 2- (1)/(2) xx 2 xx2 + (1)/(2) xx 1 xx 2`
or P= 0 or mv= 0 or v=0
Hence, kinetic energy at `(t= 45)= (1)/(2) mv^(2)= 0`