Don't know where to start on this problem

  • #1

Homework Statement


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?

Homework Equations


F = ma = m(v/t)


The Attempt at a Solution


I know that the initial force is 6.378N and after that I dont know where to go.
 

Answers and Replies

  • #2
Avodyne
Science Advisor
1,396
90
Force, acceleration, and velocity are all vectors. And acceleration is the change in velocity over the time interval.
 
  • #3
so v2 - v1/ t is the Fnet acceleration, then i dont understand how you get the force acting upon it
 
  • #4
Avodyne
Science Advisor
1,396
90
[tex]\vec{F} = m\vec{a}[/tex]

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).
 
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