What is the speed of the block after the collision?

[huynhtn2]

Homework Statement

When a bullet strikes a block of wood originally at rest, the bullet becomes embedded into the wood block which travels 1.70 m after the collision. If the mass of the bullet is 5.26 g and the mass of the block is 2.40 kg, what is the speed of the block immediately after the collision? The coefficient of kinetic friction between the block and the surface is 0.30.

Homework Equations

ke=0.5mv^2
Ffr= ukmg

The Attempt at a Solution

Ke = Ffriction
0.5mv^2= uk mg
v= square root (2(9.81)(0.3))
v= 2.43 m/s

i don't know what to do with the 1.70 m distance

 

[sylas]

Homework Statement

When a bullet strikes a block of wood originally at rest, the bullet becomes embedded into the wood block which travels 1.70 m after the collision. If the mass of the bullet is 5.26 g and the mass of the block is 2.40 kg, what is the speed of the block immediately after the collision? The coefficient of kinetic friction between the block and the surface is 0.30.

Homework Equations

ke=0.5mv^2
Ffr= ukmg

The Attempt at a Solution

Ke = Ffriction
0.5mv^2= uk mg
v= square root (2(9.81)(0.3))
v= 2.43 m/s

i don't know what to do with the 1.70 m distance

Your second formula in the attempt at a solution is comparing energy and force. The units do not match. You can only compare an energy term with another energy term, or a force with another force.

How can you get an energy value using the friction force? Thinking about this will give you the solution.

Cheers -- sylas