(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 0.39 kg particle moves in an xy plane according to x(t) = - 13 + 1 t - 6 t^3 and y(t) = 28 + 5 t - 11 t^2, with x and y in meters and t in seconds. At t = 1.0 s, what are (a) the magnitude and (b) the angle (within (-180°, 180°] interval relative to the positive direction of the x axis) of the net force on the particle, and (c) what is the angle of the particle's direction of travel?

2. Relevant equations

F(y) = ma(y)

F(x) = ma(x)

3. The attempt at a solution

Well I've got the magnitude of the force correct as 16.45N after finding the second derivative of x and y and then using Pythagoras's theorem.

What I'm struggling with is part B and C. From what I understand both answers should be the same, as the direction of Fnet should be the direction of travel.

I attempted to calculate the angle between the force and the y axis. I used sin^-1 theta = 22/28.43. This gave me a value for theta of 50.71 degrees. I then added 90 degrees to this to get the angle relative to the positive x axis. Getting an answer of 140.71 degrees for both B and C. But this is apparently wrong.

Where did I go wrong?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Particle of certain mass moving in an xy plane

**Physics Forums | Science Articles, Homework Help, Discussion**