Block sliding down an incline - Find the Work

[mb85]

In Fig. 8-49, a block slides down an incline. As it moves from point A to point B, which are 7.2 m apart, force acts on the block, with magnitude 4.4 N and directed down the incline. The magnitude of the frictional force acting on the block is 5.5 N. If the kinetic energy of the block increases by 32 J between A and B, how much work is done on the block by the gravitational force as the block moves from A to B?

http://edugen.wiley.com/edugen/courses/crs1062/art/qb/qu/c08/Fig08_49.gif

 

[xman]

how does work for a non-conservative system and changes in energy relate. use this relationship, to express the change in potential in terms of work.

 

[topsquark]

In Fig. 8-49, a block slides down an incline. As it moves from point A to point B, which are 7.2 m apart, force acts on the block, with magnitude 4.4 N and directed down the incline. The magnitude of the frictional force acting on the block is 5.5 N. If the kinetic energy of the block increases by 32 J between A and B, how much work is done on the block by the gravitational force as the block moves from A to B?

Nasty!

Some hints:

Sketch a FBD. What forces do we know are on the block? (There are 4 of them.) Which of these forces do work as the block is pushed down the incline? (3 of them do.) We know how much the kinetic energy has changed by, what does that tell us about the total work done on the object?

-Dan