A ball is thrown off a 28 m high cliff at 3 m/s, 50 degrees above the horizontal(Xaxis). How long does it take to hit the ground?

The first thing to do is to break the problem into two - treating motion in the horizontal direction independently for the motion in the vertical. Since the ball is thrown at an angle of 50 degrees above the horizontal, that means its initial velocity in the vertical direction is 3 m/s * sin(50 degrees). So the question becomes:

A ball is thrown directly upward off a 28 m high cliff at 3m/s * sin(50) m/s. How long does it take to hit he ground?

Now you can use the standard equation of motion, worrying only about the vertical components of distance, velocity, and acceleration:

d = d_0 + v_o*t + 1/2 a t^2

d = 0
d_0 = 28 m
v_o = 3 * sin(50) m/s
a = g = -9.8 m/s^2

Solve for t.

I have looked at several of Mike's questions and , in general, they can not be answered with data given. Mike has not gotten back to me so I am wondering what's up with him. In this case, like others, air density, mass of ball, humidity, etc... are all missing so no answer.

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Originally Posted by ballengerb1

I have looked at several of Mike's questions and , in general, they can not be answered with data given. Mike has not gotten back to me so I am wondering whats up with him. In this case, like others, air density, mass of ball, humidity, etc... are all missing so no answer.

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This is unnecessary, it is obviously an idealised physics question. No need to be obtuse.

Thanks for the insult, have you read all of his questions? They each lack data needed to make a calculation. None of the books I have used requires a student to make assumptions in physics. Where is Mike on this? He has not come back yet to tell us if this is an actual test question or just something he is thinking.

Quote:

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Originally Posted by ballengerb1

I have looked at several of Mike's questions and , in general, they can not be answered with data given. Mike has not gotten back to me so I am wondering whats up with him. In this case, like others, air density, mass of ball, humidity, etc... are all missing so no answer.

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I think we can assume that this is a straight-forward high school physics question, in which case it is assumed that air resistance = 0, and hence air density and the mass of the ball does not come into it.

Quote:

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Originally Posted by ballengerb1

None of the books I have used requires a student to make assumptions in physics.

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Really? Every high school text I have ever seen says that for problems like this air resistance is to be ignored. Otherwise the problem is impossible to solve without use of differential equations. From the wording of this it's safe to assume that this is indeed a question from an introductory physics text, and high school students taking introductory physics would not be exected to know how to handle differential equations.