Coefficient of friction for a sliding 15 kg box

[luxford]

Homework Statement

A small 15 kg cardboard box is thrown across a level floor. It slides a distance of 7.0 m, stopping in 3.3 s. What is the coefficient of friction between the box and the floor?

Homework Equations

The Attempt at a Solution

I didn't know how to do it. I just drew a free-body diagram of it. :|

 

[haruspex]

What forces do you have in your FBD? What is the deceleration (a) according to your forces equation and (b) according to the given data?

 

[luxford]

The forces I have on my FBD is the force of gravity, normal force, and force of friction.

As for deceleration, it is not given...

 

[haruspex]

The forces I have on my FBD is the force of gravity, normal force, and force of friction.

As for deceleration, it is not given...

You know the equation ƩF=ma, right? Apply this in the horizontal and vertical directions to obtain two equations.

 

[rude man]

Homework Statement

A small 15 kg cardboard box is thrown across a level floor. It slides a distance of 7.0 m, stopping in 3.3 s. What is the coefficient of friction between the box and the floor?

Homework Equations

The Attempt at a Solution

I didn't know how to do it. I just drew a free-body diagram of it. :|

What's the average speed? So then what's the initial speed?
Then, can we equate initial k.e. with friction energy loss to compute the friction coefficient?

 

[Dewgale]

The forces I have on my FBD is the force of gravity, normal force, and force of friction.

As for deceleration, it is not given...

If you have t, d, and v_f, you can find the deceleration using kinematics.

Since you have all three of these, finding deceleration is quite simple.

d=v_ft+$\frac{1}{2}$at²