A block of mass 2.0 kg kept at rest on an inclined plane of inclination `37^0` is pulledup the plane by applying a constant force of 20 N parallel to the incline. The force acts for one second. A. show that the work done by the applied force does not exceed 40 J. b. find the work work done by the applied force is 40 J. c. Find the kinetic energy of the block at the instant the force ceases to act. Take `g=10 m/s^2`.

Answer

A, B, C, D

Explanation

a. `m=2kg, theta=37^0 F=20N`
From the free body diagram
`F=(2gsintheta)+ma`
`rarr a=(20-20sintheta)/2=4m/sec^2`
`s=ut+1/2at^2=2m`
`(u=0, t=1s, a=1.66)`
So,workdone `W=FS=20xx2=40J`

b. If W=40J
`S=W/F=40/20=2m`
So, work done `W=-mgh`
`=020xx1.5=-24J`
c. `v=u+at`
`=4xx1=4m/sec`
So, `K.E. =1/2mv^2`
`=1/22xx16=6J`