- #1

MrMoose

- 23

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## Homework Statement

While two forces act on it, a particle is to move continuously with v = (3 m/s)i - (4 m/s)j. One of the forces is F1 = (2N)i + (-6N)j. What is the other force?

## Homework Equations

My main problem is with the verbiage, "move continuously". Does this suggest constant acceleration? If yes, then I would reference an equation for motion with constant acceleration such as:

v^2 = v02 + 2a(x - x0)

However, there's too many unknowns to use this equation (and other equations for motion). I don't know time, distance, initial velocity, or acceleration.

## The Attempt at a Solution

My thought process:

1. Find accelerations (a)i and (a)j using equation for motion and given velocity vector (It would have to be in terms of variables since there's several unknowns)

2. Find total forces (F)i and (F)j on the particle using F = ma (again, it would have to be in terms of 'm' since I don't know the mass). Unknowns cancel out in the end?

3. Take the difference between the total force vector F and F1 to determine F2

This seems like a very convoluted path to take and I'm pretty sure it's not correct. What am I missing from the initial problem statement? I feel like there's more information there that I'm not getting.

The answer is F2 = (-2N)i+(6N)j

This confuses me. How can you have an object in motion if two equal and opposite forces are acting on it? Shouldn't it be stationary? It makes me think that this is more of a conceptual problem than a calculation intensive problem. Thanks for your help in advance - MrMoose