Solving Momentum Collision: Finding Velocity of Sliding Blocks | Homework Help

[runningirl]

Homework Statement

A small (35 g) block is sliding toward the right along a table when it hits a larger (90g) block that was at rest. After the collision, the large block slides 72 cm to the right before coming to a rest , while the small block bounces off the large block, sliding 1.5 m to the left before stopping. The somewhat rough table has a coefficient of kinetic friction of 0.42. What is the velocity of the small block just before it hits the larger block?

Homework Equations

The Attempt at a Solution

so i have to find the final velocity of the larger block...
which could be .72(.42)(.09)?

then i use the conservation of momentum equation?!

 

[Azelketh]

you could consider conservation of energy.

The inital block has energy
$$Ke= \frac{1}{2} m v^2$$
where v is its velocity
m is the mass.

The second block has lost all its energy overcoming the friction of the table by the time it comes to rest.

As Work done = force*distance

friction force = mass of object* acceleration due to gravity * friction coefficient

can you solve from there?

 

[runningirl]

yes, thanks so much!