Thursday

August 28, 2014

August 28, 2014

Posted by **Dreskillz89** on Tuesday, September 22, 2009 at 10:02am.

Can you check if I am doing this right?

I had

v(initial) = 20 m/s

g = 9.8 m/s^2

x = 24m

1st I solved for time:

x = v(initial) t

x = v(initial) cos(theta) t

24 = 20 cos(theta) t

24 / [20 cos(theta)] = t

Y-motion

y = v(initial) sin(theta)*t - (1/2)gt^2

0 = [20sin(theta)]*[24 / 20cos(theta)] t -(1/2)(9.8)[24 / 20cos(theta)]^2

0 = 24tan(theta) - (7.056/cos^2(theta))

7.056 = 24tan(theta)cos^2(theta)

7.056 = 24sin(theta)cos(theta)

<then I divided both sides by 12 to get a trig identity>

.588 = 2sin(theta)cos(theta)

.588 = sin2(theta)

theta = arcsin(.588) / 2

theta = 18.008 <--answer

Is that how you would do it? Is that the correct answer?

- Physics -
**drwls**, Tuesday, September 22, 2009 at 11:56amI will skip the derivation and cut to the final equation for horizontal range X:

X = (V^2/g)sin 2A

where A = the launch angle.

24 = (400/9.8) sin 2A

sin 2A = 0.588

2A = 36 or 144 degrees

A = 18 or 72 degrees

Looks like you did it right. Consider the possibility of two solutions.

**Related Questions**

Physics - An object m is released from the top of an inclined, frictionless ...

Physics - An object is projected at an angle of 53.1degrees above the horizontal...

Physics - An object is projected at an angle of 53.1degrees above the horizontal...

trig - Find csc(theta), tan (theta), and cos (theta), where theta is the angle ...

Physics Urgent please help - A physical pendulum consists of a body of mass ...

physcs (Geometry bit) - how do you prove that an object on a ramp resolved into ...

Physics - An object is projected from ground level with launch speed u and at an...

physics - a shot-putter throws the shot with an intial speed of 14 m/s at a 40 ...

physics to be solved ..easy !! - A shot putter launches a 6.910 kg shot by ...

Physics - Imagine a right-angle triangle with angle θ = 40o on the left. ...