Physics 163

Unit 3: Motion in Two-Dimensions

Problem Set D

Problem 11:

A ball is thrown straight upward and returns to the thrower's hand after 3.5 s in the air. A second ball is thrown at an angle of 33.3 degrees with the horizontal. At what speed (in m/s) must the second ball be thrown so that it reaches the same height as the one thrown vertically?

• Read the problem carefully and diagram the physical situation (trajectory diagram)
• Identify known and unknown information in an organized manner (x-y table)
• Take the time to plot out a strategy prior to beginning the solution
• Identify an appropriate formula to use
• Perform step-by-step algebraic manipulations

 Vertically Thrown Ball Ball Thrown at Angle Vertical Horizontal Vertical y = ??? viy = ??? ttotal = 3.5 s tup = 1.75 s ay = -9.8 m/s/s vfy = 0 m/s (@ t = 1.75 s) Not Important to this Problem y = ??? viy = vi • sin() ay = -9.8 m/s/s vfy = 0 m/s (@ peak) t = ???

A discussion of the formulae for projectile motion, of the trajectory characteristics and of the basic strategy for solving such problems is provided on the Set D Overview Page.

Detailed information about and discussion of the strategies for solving non-horizontally launched projectile problems is provided online at The Physics Classroom.

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