# Homework Help: Acceleration and Momentum.

1. Feb 17, 2016

### Meezus

1. The problem statement, all variables and given/known data
A vehicle has a mass of 600 kg. Its engine provides a forward force of 1500 N, but the motion is resisted by a constant frictional force of 300 N.
Calculate a) the acceleration of the vehicle,
b) its momentum 6.0 s after starting to move.

2. Relevant equations
F=ma
a=f/m
Change in Moment = Force x Time.

3. The attempt at a solution
using a=f/m i can get acceleration easily.
1500 - 300 = 1200
1200 / 600 = 2.
a = 2 m/s^2

I think part B revolves around Change in Moment = Force x Time but I'm not sure as I can't see anyway to work it out using that formula but I'm unaware of another formula having time and monument in it.
Time = 6.
Force = 1200.
6 x 1200 = 7200?

2. Feb 17, 2016

### ehild

Remember the definition of momentum p=mv, and how is the velocity related to acceleration and time.

3. Feb 17, 2016

### Meezus

acceleration = change in V / t?

4. Feb 17, 2016

### ehild

yes, so what is the velocity after 6 s?

5. Feb 17, 2016

### Meezus

a x t = change in V.
2 x 6 = 12.
p=m x v
12 x 600 = 7200?

6. Feb 17, 2016

### ehild

Yes, but do no forget the unit. What is it?
You see, it is the same result.

7. Feb 17, 2016

### Meezus

7200 kg.m/s?

8. Feb 17, 2016

Correct.