Two balls thrown at the same speed from the same height

  • Thread starter pelmel92
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  • #1
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Homework Statement



Two balls are thrown with equal speeds from the top of a cliff of height h. One ball is thrown at an angle of α above the horizontal. The other ball is thrown at an angle of β below the horizontal. Show that each ball strikes the ground with the same speed. (Do this on paper. Your instructor may ask you to turn in this work.)

Find that speed in terms of h and the initial speed v0. (Ignore any effects due to air resistance.) (Use any variable or symbol stated above along with the following as necessary: g for the acceleration due to gravity.)
v =

Homework Equations



V= at + v_0

The Attempt at a Solution



v=√(v_0^2cos^2(ø) +[h/t]^2)

im just plain stuck here... not even sure if im interpreting the q correctly, and if i am then i can't figure out how to get rid of that time variable... HELP
 

Answers and Replies

  • #2
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You basically want to write an equation for the velocity of each ball, and show that at a height of zero they are equal. You are only concerned with the vertical component, so this will involve using the sine function.

Remember that measuring from the horizontal, sin(a) is a positive quantity and sin(β) is negative. Also, I think you should use this equation:

x-x0=vt + 1/2at2 where a = -9.8m/s/s.
 

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