Question

A block of mass 3 kg is pulled up on a smooth incline of angle `37^@` with the horizontal. If the block moves with an acceleration `2(m)//(s^2)`, find the power delivered by the pulling force at time 5 s after the motion starts. What is the average power delivered during the 5.0 s after the motion starts?

Answer 1

Let `F` be a pulling force.
`F-30sin37^@=3a`
`F-30xx(3)/(5)=3xx2`
`impliesF=24N`
After 5 s, velocity
`v=u+at=0+2xx5=10(m)//(s)`
The power delivered by F at `t=5s`
`P=Fv=24xx10=240W`
Displacement of block in 5 s
`s=(1)/(2)at^2=(1)/(2)xx2xx5^2=25m`
Work done by pulling force in 5 s.
`W=F_S=24xx25=600J`
The average power delivered by pulling force .
`overlineP=(W)/(t)=(600)/(5)=120W`