Don't know where to start on this problem

1. Sep 8, 2007

Warpedintellect

1. The problem statement, all variables and given/known data
A 1.25-kg object is moving in the x direction at 17.4 m/s. Just 3.41 s later, it is moving at 26.8 m/s at 34° to the x axis. What are the magnitude and direction of the force applied during this time?

2. Relevant equations
F = ma = m(v/t)

3. The attempt at a solution
I know that the initial force is 6.378N and after that I dont know where to go.

2. Sep 8, 2007

Avodyne

Force, acceleration, and velocity are all vectors. And acceleration is the change in velocity over the time interval.

3. Sep 8, 2007

Warpedintellect

so v2 - v1/ t is the Fnet acceleration, then i dont understand how you get the force acting upon it

4. Sep 8, 2007

Avodyne

$$\vec{F} = m\vec{a}$$

But I don't think you get the vector part, which is key. You should start this problem by asking yourself these questions:

What is the x component of the initial velocity?
What is the y component of the initial velocity?
What is the x component of the final velocity?
What is the y component of the final velocity?

Given the answers, you should be able to compute the x component of the acceleration and the y component of the acceleration. Then, the x component of the force and the y component of the force. Then, the magnitude of the force and its direction (expressed as an angle relative to the positive x axis).

Last edited: Sep 8, 2007