ENERGY PROBLEMS

Ex) An object slides across a horizontal table which changes its kinetic energy from 20 J to 18 J in 2 sec. How much work does the object do against friction?

* The Work Energy Relationship

The work done on or by a system = _______________________________

Wf - work done against friction

Ex) A 10 kg frictionless cart is resting on a horizontal table. A force of

10 N is applied to the cart for a distance of 8 m. What is the cart's new kinetic energy?

Ex) 100. Joules of work is needed to lift a 100. kg object from the ground. What is the object's new PE?

Ex) A crate is pulled 6m up an incline with a force of 50. N. If the PE of the cart increases by 250 J. What is the total work done against friction in moving the box?

W = DKE = DPE + Wf

W = F × d

Ex) 4 N force is exerted on a 1kg mass at rest causing it to move 2 m

A. Find the object's K.E.

B. Find the objects velocity

Ex) A force of 100. N lifts the object 10. m off the ground. What is the object's new potential energy?

What is the mass of the object?

Ex) A spring has a spring constant of 2 N/m. How much work must be done to stretch 5m from its equilibrium position?