# Calculate force of friction on car as it rolls across

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1. Jun 8, 2015

### SelenaT

1. The problem statement, all variables and given/known data
Calculate the force of friction on a toy car as it rolls across a flat floor.

Given:
mass = 0.293kg
time = 3.66 s
displacement = 8.7

2. Relevant equations

Fnet = mass x acceleration

displacement = [(velocity1 + velocity2)/2] time

velocity2 = velocity1 + acceleration(time)

3. The attempt at a solution
Step 1

displacement = [(velocity1 + velocity2)/2] time
v2 = (2d/time) - v1
= 2(8.7m)/3.66s - 0m/s
= 4.75m/s

Step 2
velocity2 = velocity1 + acceleration(time)
a = v2-v1 / time
= 4.75/3.66
= 1.29m/s^2

Step 3
F=ma
= 0.293kg x 1.29m/s^2
= 0.38N

so the force of friction on the car is 0.38N ?????

I am unsure if this is right and if i have to use the Force of friction = μ x N equation

2. Jun 8, 2015

### billy_joule

The problem statement is incomplete. Please copy the entire question word for word.

3. Jun 8, 2015

### SelenaT

Will remember to add background of the question.

"Calculate the force of friction on your car as it rolls across a smooth level surface."

Not sure why it says smooth level surface since there was friction between the car and the floor but...

This is a follow up question to an experiment we did. We had to make a mousetrap car so the car was powered only by the mousetrap. The mass of my car is 0.293kg and it travelled 8.7 m in 3.66 seconds across a flat floor.

4. Jun 9, 2015

### billy_joule

Ok. The missing information is that the car comes to a stop after travelling the 8.7 metres.

What you've done is correct.

5. Jun 9, 2015

### haruspex

Are the distance and time measured from a point where the mousetrap has ceased to supply any power?

6. Jun 9, 2015

yes

7. Jun 9, 2015

Ok