Change in kinetic energy question... (1 Viewer)

[miss_b]

Could anyone help me with this question?

A child uses a broomstick to push a 2.0kg bucket of water across a floor. The broomstick is held at an angle of 60 degrees to the horizontal and exerts a force of 100N on the bucket. The bucket is initially at rest and encounters a constant frictional force of 10N while moving a distance of 5.0m

Calculate the change in kinetic energy of the bucket during this interval

Thanks

 

[Xayma]

Ok the work done is the change is in energy of the sytem.

ΔE_k=W
=Fdcosθ
=(100*cos 60°-10)*5 [only the force moving changes the kinetic energy and hence work done (as far as this is concerned]
=40*5
=200J

The change in kinetic energy is 200 Joules

 

[miss_b]

Thanks for the help

 

[Xayma]

NB: You could also do it by calculating the force on the bucket (50N resulting in acceleration) convert this to acceleration, work out the time taken for it to cover the distance using the formulas with u=0, than the final velocity, and then calculate the final kinetic energy after figuring out the final velocity. Or just use the work formula