Question

I have a small question in the application of Work-Energy theorem. 

Q) A block of mass 5 Kg is attached to a spring of spring constant 4000N/m. It is stretched by a distance of 100 mm from its mean position. Then the block is released. What will be the speed of the block when it passes the mean position again? The surface has a coefficient of friction = 0.2 

My answer: By Work energy theorem,    Work done by friction + Work done by applied force + Work done by spring = Change in Kinetic Energy
However the answer in my book says  Work done by friction  + Work done by spring = Change in Kinetic Energy

Why don't we consider work done by applied force? 

Thanks! 

Read 1 Solution.

Alright..the solution is very simple....

According to work energy theorem , NET work done equals change in kinetic energy ....the applied force is ignored in this case because the velocity of the block after release of the block from rest is asked ....(Read slowly!!) Hence your book becomes right in this case. thus only frictional force and the force exerted by the spring comes into picture!!!!!!!!!!!

 

CHEERS!!!!!

AJAY RAMAKRISHNAN 10 year ago is this solution helpfull: 0 0

Submit Your Answer


please login to submit your answer

Login Here

Register