# Homework Help: Finding velocity using given angle

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1. Jul 28, 2015

### dahano

1. The problem statement, all variables and given/known data:
A body is projected with 50m/sec at an angle of 53 degree with the horizontal. After what time velocity makes an angle 33.7 degree with horizontal. (tan 33.7 = 2/3)

2. Relevant equations: Mostly from 2-Dimension and maybe calculus.

3. The attempt at a solution: I've first picked up the second part of the question and tried to find out the height at 33.7 degree angle by using h = uSinθt - 1/2gt but in this, I can't decide that what u should I put because 50m/sec is at the ground level. Moreover, I also don't know the time, t. And thus this method can not be used. What could be the other way? Please guide me in layman's term.

2. Jul 28, 2015

### yango_17

Take into consideration that the motion consists of both x and y components (x=vcosθ and y=vsinθ). Perhaps you could try calculating what the initial speed and final speeds are for the y component. Then try calculating how much time it would take for that change in speed using your other kinematics formulas.

3. Jul 28, 2015

### dahano

Yep, that worked! I've got 2 seconds as the answer and hopefully it must be correct. Thanks :-)

4. Jul 28, 2015

### haruspex

I confirm 2 sec. (More precisely, 2.03, using 9.8 for g.)