A block initially at rest is pushed horizontally along a frictionless surface with a constant force.
After moving a distance d the speed of the block is v. What is the speed of the block after being
pushed a distance 2d?

Question

A block initially at rest is pushed horizontally along a frictionless surface with a constant force.
After moving a distance d the speed of the block is v. What is the speed of the block after being
pushed a distance 2d?

anonymous · Answer

|dw:1332218402528:dw|
workdone by the force on the block=change in kinetic energy of the block
F*d=1/2mv^2-0
m=2Fd/v^2
therefore 
        similarly       F*2d=1/2mV1^2-0
                         =>2Fd=1/2*(2Fd/v^2)V1^2
                         =>V1=sqrt(2)*v......answer