Box on Inclined Plane (with Friction)

[B. variegatus]

Homework Statement

A crate of mass 9.2 kg is pulled up a rough incline with an initial speed of 1.52 m/s. The pulling force is 110 N parallel to the incline, which makes an angle of 20.6° with the horizontal. The coefficient of kinetic friction is 0.400, and the crate is pulled 4.94 m.

(e) What is the speed of the crate after being pulled 4.94 m?

Homework Equations

F(f)=mu*N
E(k)=(mv^2)/2
U=mgh
delta E(k)= E(k1) - E(k2)
W=F*d
d=(a*t^2)/2

The Attempt at a Solution

W=(m*v(f)^2)/2
v(f)=sqrt(2W/m)
W=110*4.94=543.4J
v(f)=sqrt(543.4*2/9.2)=10.87ms^-1

The computer says that this is wrong though?

 

[PhanthomJay]

Homework Statement

A crate of mass 9.2 kg is pulled up a rough incline with an initial speed of 1.52 m/s. The pulling force is 110 N parallel to the incline, which makes an angle of 20.6° with the horizontal. The coefficient of kinetic friction is 0.400, and the crate is pulled 4.94 m.

(e) What is the speed of the crate after being pulled 4.94 m?

Homework Equations

F(f)=mu*N
E(k)=(mv^2)/2
U=mgh
delta E(k)= E(k1) - E(k2)
W=F*d
d=(a*t^2)/2

The Attempt at a Solution

W=(m*v(f)^2)/2
v(f)=sqrt(2W/m)
W=110*4.94=543.4J
v(f)=sqrt(543.4*2/9.2)=10.87ms^-1

The computer says that this is wrong though?

total work is change in KE. You just gave the final,not the change. Also, more forces besides the applied force do work. You need to identify work done by all forces.