ilovephysics.com :: free online physics help, tutorials, forums, classes, misconceptions in / Answer in solutions manual with work on a ramp doesn't seem correct

Sancrist · 2008-03-12 04:14:56

Problem from Glencoe Principles and Problems, pg 279 #70

Maricruz slides a 60.0 kg crate up an inclined ramp that is 2.0 m long and attached to a platform 1.0 m above floor level. A 400.0 N force, parallel to the ramp, is needed to slide the crate up the ramp at a constant speed.

a) How much work does Maricruz do in sliding the crate up the ramp

Answer manual says 800 N

What I am doing is this. I know the ramp has a length of 2m, she supplies 400N of force, and the height of ramp is 1 m.

I find the angle of the incline to be 30 degrees, and multiply her force of 400N by 2m by sin 30

This gives me an answer of 400 J.

Who is wrong.... the book or me?

Chris · 2008-03-19 20:24:56

Who is wrong.... the book or me?

Sorry, but you are wrong.

The force being applied by Maricruz is 400 N. Maricruz displaces the box 2 meters. The angle between the applied force and the displacement is 0 degrees.

This is a common mistake. The angle in the following:

$W = F \, d \, sin (\theta)$ ,

is the angle between the force vector and the displacement vector. In this case, the force is being applied completely in the same direction as the displacement.

Giancoli is just trying to trick you with all that talk of angles and inclines.

Announcement

#1 2008-03-12 04:14:56

Answer in solutions manual with work on a ramp doesn't seem correct

#2 2008-03-19 20:24:56

Re: Answer in solutions manual with work on a ramp doesn't seem correct

Board footer