Homework Help: Projectiles Question

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1. Jul 14, 2014

rr96

1. The problem statement, all variables and given/known data

As part of a NASA experiment, golfer Tiger Woods drives a golf ball on the moon, where
g = 1.60 m/s2. He ‘launches’ a golf ball with a speed of 285 km/h, at an angle of 42o with the horizontal. What horizontal distance will his drive travel before landing back on the surface of the moon. Ignore the curvature of the moon.

2. Relevant equations

d = (Vi)(t) + 1/2(a)t2

Vf =Vi + at

3. The attempt at a solution

Initial horizontal velocity:

285 x cos42
= 211.8 km/h

Initial Vertical Velocity

285 x sin42
= 190.7 km/h

Finding time using vertical components

d = (Vi)(t) + 1/2(a)t2

0 = 190.7t - 4.9t2

t = 38.9 s

Using time to find distance

d = (Vi)(t) + 1/2(a)t2

d = 211.8 x 38.9 + 1/2(0)t2

d = 8239 m

2. Jul 14, 2014

haruspex

4.9?

3. Jul 14, 2014

rr96

Sorry, I skipped a step. 1/2 x 9.8 = 4.9

4. Jul 14, 2014

Nathanael

Haruspex is a smart guy, I'm sure he could see the step you skipped.

His next question would be:

"9.8?"

5. Jul 14, 2014

Nathanael

Besides that, though, there's one more small problem. Your units are inconsistent.

(You need to convert km/hr to meters/second)

6. Jul 14, 2014

rr96

Thanks! I completely missed that. My final answer is 635 m

7. Jul 14, 2014

Nathanael

How long will the ball be in the air? (What was your calculation for this?)

8. Jul 14, 2014

rr96

10.8 s ?

Last edited: Jul 14, 2014
9. Jul 14, 2014

rr96

d = (Vi)(t) + 1/2(a)t2

0 = 52.97t - 4.9t2

t = 10.8 s

10. Jul 14, 2014

Nathanael

Have you forgotten where this is taking place? :) Remember, we're not on Earth.

11. Jul 14, 2014

rr96

d = (Vi)(t) + 1/2(a)t2

0 = 52.97t - 0.8t2

t = 66.21 s

I had forgotten! Thank you so much!

12. Jul 14, 2014

rr96

13. Jul 14, 2014

Nathanael

There you go, that should be the correct answer.

(Do you have something that says what the correct answer is?)

14. Jul 14, 2014

rr96

Yup! That's what it says the answer is.

15. Jul 17, 2014

Dumbledore211

You have missed out on crucial piece of information which the value of is 1.60m/s^2 as the event is taking place on the moon