## ahGhH! Pls help! I've jst joined this forum and i need help on a Projectile Motion q!

umm... i'm not really used to using forums.. but whoever is online now and reading this... i would reaLLY appreciate if you could help me on this question.. this is fairly uRGent because its a bonus question which i want to hand in early tomorrow.

Okay, here is the question:

A golfer is standing at the top of a hill that slopes downward at a 45 degree angle. If he hits his golf ball with an initial velocity of 30.0m/s forward, what distance (d) down the slope from him does the ball first strike the hill?

(sorry i can't draw the diagram here but if you dont understand the question i'll try to add a pic or sketch)

thanks..! [t)]
 PhysOrg.com science news on PhysOrg.com >> City-life changes blackbird personalities, study shows>> Origins of 'The Hoff' crab revealed (w/ Video)>> Older males make better fathers: Mature male beetles work harder, care less about female infidelity
 oh yes.. the answer i got was 259.75 metres... is that correct?
 i'll show my work here.. although i must admit it's hard to do all these formulas on the computer.. [s(] SOLUTION (i know this format is weird, but my physics teacher wants it in this format.. ps, i am doing this in components and i am not taking into consideration significant figures) Let "up" and "forward" be positive, and "time zero" be the instant the golf ball is hit. (also let A repressent acceleration, V be velocity, T be time, x be the x-components and y be the y-components) Horizontal Motion: Xo = 0 m Vox = 30.0 m/s Ax = O m/s2 X = Xo + VoxT - 1/2 AxT2 X = 30.0T Vertical Motion: Yo = 0 m Voy = 30.0 m/s Ay = -9.8 m/s2 Y = Yo + VoyT - 1/2 AyT2 Y = -4.9t2 Since the hill is sloping downwards at an angle of 45 degrees, the X and Y component should be perpendicular, and the other angle should be 45 degree as well. Thus the X and Y components can be equated (is this right?): 30.0T = -4.9T2 T = 6.122s (must be positive) Therefore sub back into equation: X = 30.0T X = 183.67 m Y = -4.9T2 Y = -183.67 m Therefore to find distance (d) of the hill, use pythagorean theorum: d2 = X2 + Y2 d2 = (183.67)2 + (-183.67) d = 259.75 m *sigh* that was long.. blah.. can anyone tell me if that was right please??? thanks :o)

## ahGhH! Pls help! I've jst joined this forum and i need help on a Projectile Motion q!

isnt there anyone online??? [8)]
 Mentor Yep, you got the right answer - and just as a rule of thumb, even at night (when a lot of people are on) it usually takes an hour or two for a response. And its probably just a typo (you didn't use it): Voy=0.
 Recognitions: Gold Member Science Advisor Staff Emeritus I agree with Russ_Watters although I would not necessarily have interpreted "initial velocity of 30.0m/s forward" to mean exactly horizontal. Of course, given the information, that's the only interpretation you can make- but I would have worried about it! By the way, dar|{anGel_, please don't expect people to answer your questions instantly!
 um.. heh.. heh.. heh.. well, as i said, i wAS new to the forum and i was desperate to get the answer because i was about to give up on it since i worked on it for so long, and it wasnt until i realized that the angle being 45 degrees meant that the X and Y would be equal that i figured it out... (i was doing to question according to a diagram given along with the question, which was reaLLY misleading, because it made the 45 degree angle really small, and therefore the X looked longer than the Y) .. of course later, i realized it was so easy.. coz all you had to do was equate the two equations to get the time.... i mean, the method was easier than i thought it would be because i assumed that it would require a lot more work (since it was a 'bonus' question given to my Gr. 12 Physics class, and i expected something reaLLY hard.. i guess if the angle was not 45 degrees it would be a lot harder.. but not impossible) well.. i diDnt expect "instantly".. just within.. like.. minutes.. since you guys are soOOOooo presumably smart (was it wrong to overestimate your abilities?) oh yes, and that was a typo.. the Voy was supposed to be zero.. (i copied and pasted it.. and forgot to change it) Anywayss... Thanks a lot, russ_watters and HallsofIvy!! i am completely and utterly humbled by your presence and superfluous amounts of knowledge in Physics [:)] (in other words, i'll just assume you guys are hard core Physics junkies with either too much time on your hands or are just really, really nice [;)] ) if you noticed, im not exactly a Physics type person, but i like to blab on about nothing a lot (anyways, it looks like i'll become a permanent resident of your forum..i'll probably need it for the rest of my Physics-engrossed year)

 Similar discussions for: ahGhH! Pls help! I've jst joined this forum and i need help on a Projectile Motion q! Thread Forum Replies Introductory Physics Homework 3 Introductory Physics Homework 3 Introductory Physics Homework 1 Introductory Physics Homework 3 Introductory Physics Homework 4