Work-Energy Theorem: Compare W to ΔE

Topics and Files

Mechanics Topic

Work-energy theorem, conservation of energy

Capstone File

32 Work and Energy.cap

Equipment List

Introduction

The purpose of this lab is to compare the work done on an object to the change in kinetic energy of the object. Use the force sensor to measure the force applied to the cart. Use the photogate/pulley system to measure the motion of the cart as it is pulled by the weight of the hanging mass. Use Capstone to record and display the force, motion, work done, and the calculation of kinetic energy. Compare the work done to the change of kinetic energy.

Background

For an object with mass m that experiences a net force F_net over a distance d that is parallel to the net force, the equation below shows the work done.

( 1 )

W = F_netd

If the work changes the object's vertical position, the object's gravitational potential energy changes. However, if the work changes only the object's speed, the object's kinetic energy changes as shown in the second equation where W is the work, v_f is the final speed of the object and v_i is the initial speed of the object.

( 2 )

W = Δ KE = KE_f − KE_i =

mv_f² −

mv_i²