# Introductory Momentum problem

1. Dec 28, 2009

### majormuss

1. The problem statement, all variables and given/known data

Can someone help me solve this Physics question(about momentum)....?
A 2.0 Kg body is initially travelling at a velocity of 40 meters/sec East, If a constant force of 10 Newtons due East is applied to the body for 5 seconds , the final speed the body is?

2. Relevant equations
Am not sure

3. The attempt at a solution
My own answer to this question was 65m/s.... I manipulated Newton's second law...a=F/mass,,, and I got ....v2(final velocity) = Ft/m- v1. Pls explain if your answer is different.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Dec 28, 2009

### RoyalCat

That's correct!
Applying a constant force $$\vec F$$ on a body of mass $$m$$ provides that mass with an acceleration given by Newton's Second Law: $$\vec a = \frac{\vec F}{m}$$
And from there, you can just use kinematics to find the final velocity.

A second, equivalent approach would be to use the impulse-momentum theory.
That is, $$\int \vec F dt=\vec P_f -\vec P_i$$

3. Dec 28, 2009

### Redbelly98

Staff Emeritus
Just want to add, if your class is studying momentum right now then it would be beneficial to solve this problem using the impulse formula. It is likely that the goal of this exercise is to give you practice using impulse in calculations.