As defined in Chapter 7, the work done by a force on an objectis equal to the force times the displacement times the cosine ofthe angle between the force and displacement vectors(W=F·d cos(θ)).
Suppose you are supporting a 1.56-kg block. What is thegravitational force (magnitude and direction) acting on theblock?
If you lower the block a distance of 0.208 m, what is the workdone by the gravitational force as you lower the block?
What is the value of the angle θ (in degrees – do not enterunits)?
What is the change in the gravitational potential energy as youlower the block 0.208 m? (If the potential energy increases, theanswer should be positive. If the potential energy decreases, theanswer should be negative.)
Let’s switch gears and ask about the electrical force on acharged object. Suppose you have a region where the electric fieldhas a magnitude of 23.1 N/C, the field points straight down, andthe field is uniform (ie., the magnitude and direction are the sameeverywhere in this region). You place an object which has a chargeof +0.251 C in this field. What is the magnitude and direction ofthe electric force acting on the object?
Suppose you lower the object a distance 0.208 m (in the samedirection the field is pointing). What is the work done by theelectrical force as you lower the block?
What is the change in electric potential energy as you lower theobject 0.208 m? (If the electric potential energy increases, theanswer should be positive. If the electric potential energydecreases, the answer should be negative.)
This discussion is closed.
