# How fast will the car now move?

1. Aug 8, 2014

### max1020

A 100kg cart is moving at 2.3m/s. A machine has been designed to apply a force of 1200N over a distance of 0.52m as this cart passes by. How fast will the car now move?

3. The attempt at a solution
I used a=fnet/m where fnet was 1200-0 so the answer I got was 2307.68 m/s^2. Is this right?

2. Aug 8, 2014

### Nathanael

Why did you divide the force by the distance?

Is newton's law "Force = distance times acceleration" or is it "Force = mass times acceleration"?

Anyway, that gives you (if you do it correctly) the acceleration of the object, but the question didn't ask for the acceleration. You'll need to use the acceleration to find the final velocity.

Do you know about Work and Energy? (If not, that's fine, there are other ways to solve it.)

3. Aug 8, 2014

So a= 2.3m/s

4. Aug 8, 2014

### Nathanael

Look at the units. Acceleration does not have units of m/s. Acceleration has units of m/s^2

Do you know newton's definition of force? (Also known as "Newton's Second Law")

It says:
Net Force = Mass times acceleration

Therefore (if you rearrange that definition)
Acceleration = Force divided by mass

5. Aug 8, 2014

1200/100
=12 m/s^2

V=3.84

6. Aug 8, 2014

### Nathanael

Yes, that is correct.

7. Aug 8, 2014

### max1020

I used v^2= u^2+2as
=sqrt(2.3^2 + 2 x 12 x 0.52)
=3.84

8. Aug 8, 2014

### max1020

Whoops is it 4.215

9. Aug 8, 2014

### Nathanael

Yes, that is the correct answer.

10. Aug 8, 2014

Thank you!