Quick question about work and forces(incline plane)

Homework Statement

A block of mass is pushed up an incline
of width d and height h with coefficient of friction μk
up to the top of the incline by a constant applied force of
magnitude F parallel to the ground. The block begins
at rest.

f=ma

w = f . d

The Attempt at a Solution

if i choose a coordinate system with an x axis Parrnell to the incline plane, then would it go like this:

normal force work= 0

applied force work = Fd/cos(60) <-- not sure about this one, my prof just wrote Fd in class, but i didnt understand why

work by fric = -ukmgd

work done by gravity = -mgh

is this right?

PhanthomJay
Homework Helper
Gold Member

Homework Statement

A block of mass is pushed up an incline
of width d and height h with coefficient of friction μk
up to the top of the incline by a constant applied force of
magnitude F parallel to the ground. The block begins
at rest.
What is the question?

f=ma

w = f . d

The Attempt at a Solution

if i choose a coordinate system with an x axis Parrnell to the incline plane, then would it go like this:

normal force work= 0
this is correct applied force work = Fd/cos(60) <-- not sure about this one, my prof just wrote Fd in class, but i didnt understand why
where did the 60 come from? And work is not fd/cos theta. Work is force times displacement times the cos of the angle between the 2. And if d represents the base width of the incline, the distance along the incline is from heel to toe is greater than d.
work by fric = -ukmgd
if you are calling d the distance traveled along the incline, then yes, correct.
work done by gravity = -mgh
yes, correct, that is the work done by gravity from the bottom to top of the incline
is this right?
Please post the question exactly as written and perhaps as illustrated.

the question is just to find the work done by each of the forces, just really to find the expression for each individual force. i modified the applied force (F), because it is not parallel to my chosen coordinate system, it is parallel to the ground.(picture on its way)

http://s861.photobucket.com/albums/ab174/alkaline262/?action=view&current=inclineplanejpg.jpg

i actually know think work done by Force applied = Fsin(theta)d

:D

Last edited:
PhanthomJay