# Find the coefficent of friction of one block

1. Two blocks are connected by a light string that passes over a frictionless pulley as in the figure. The block of mass 8.24 kg lies on a horizontal surface and is connected to a spring of force constant 335 N/m. The system is released from rest when the spring is unstretched.
If the hanging 14.7 kg block falls a distance 0.653 m before coming to rest, calculate the coefficient of kinetic friction between the block m1 and the surface. The acceleration of gravity is 9.8 m/s^2

## Homework Equations

m2gh=m1gμ - 1/2 kx^2

## The Attempt at a Solution

as the equation says, i just try to solve for the coefficient of friction by substituting the values. am I wrong?

lewando
Homework Helper
Gold Member
The units of your stated equation are not consistent. Therefore, that equation is wrong. How did you come up with that equation?

well, m1gmew is because the gravity acts down on it, mew is against it so everything acts on that fragment of the system, then the m2gh is the same but now with the height actin too, and then the hook's law is just subtracting from the system

lewando
Homework Helper
Gold Member
Your equation is messed up because you have: [energy] = [force] - [energy]. If you are going to do this problem using an energy balance, what is the energy gained or lost from the 3 components?

energy+energy= force?

lewando
Homework Helper
Gold Member
Seriously, no.

1. What is the energy gained (or lost--please specify so I know you are paying attention ) by the spring?
2. What is the energy gained (or lost--please specify--same reason) by m2?
3. How much engery is required to move m1 over the stated distance?

How would they balance?

well, wouldn't it be, energyrequired to move m1= energyspring-energym2 ?

lewando
Homework Helper
Gold Member
Consider this: Ʃ(energy sources) = Ʃ(energy sinks).

What are the energy sources? Sinks?