Velocity -time graph for a body of mass 10 kg is shown in figure. Work -done on the body in first two seconds of the motion is :

Options

A. 12000 J
B. `-12000` J
C. `-4500` J
D. `-9300 `

Answer

C

Explanation

Given ,equation of line .
`v = - 5t +50`
at `t = 0 , u = v +50 ` m/s
At `t = 2 s , v ( t = 2) = - 5 xx 2 + 50 = 40 ` m/s
` W = DeltaK.E = 1/2 mv^(2) =-1/2 "mu"^(2) = 1/2 xx10(40)^(2) - 1/2 xx10(50)^(2)`
`W = - 4500` J .