# Homework Help: Block pulled on horizontal surface -w/friction-

1. Oct 2, 2011

### bdragons

1. The problem statement, all variables and given/known data
A box weighing 80N is pulled along a horizontal surface by a force of 15 N which is directed at 20° above the horizontal. If the box started from rest and the coefficient of friction is 0.15, find the kinetic energy and velocity of the box after it traveled a distance of 10 m.

2. Relevant equations
Normal force= W-Tsinθ
Frictional force=μk x Normal force

3. The attempt at a solution
First I looked for normal force which turns out as 74.87 then frictional force which is 11.23 after that, I dont get how to find velocity. I just need final velocity at this point to get average velocity=velocity then having V, I could solve for K.E.

Last edited: Oct 2, 2011
2. Oct 2, 2011

### Uniquebum

Force accelerates the box's speed.
It has a speed of 0m/s in the beginning.
$x = x_0 + v_0t + 0.5at^2$
$x = 0.5at^2$
On the other hand
$v_{end} = v_0 + at$
$v_{end} = at$
Should be all the info you need. Think about it.

3. Oct 2, 2011

### bdragons

would just like to clear the following things:
-what does x,x0,v0 stand for? (guessing that 0 there means zero)
-does a stand for acceleration while t is time?

4. Oct 2, 2011

### Uniquebum

They're the basic equations of motion.
x = total distance
x_0 = distance from origin(usually 0 unless origin is set somewhere else than on the system you're investigating)
v_0 = speed the system has when you begin investigating it
a = acceleration
t = time

5. Oct 2, 2011

### Staff: Mentor

If you know the net force F moves the block, acting in the direction of motion, then the work done on the block moving it distance d is given by F*d. Where does that work end up (how is it expressed in the system)?