Projectile Motion ball is thrown upward

  • Thread starter creynaud
  • Start date
  • #1
4
0

Homework Statement


A ball is thrown upward at an angle of 30° to the horizontal and lands on the top edge of a building that is 20 m away. The top edge is 5.0 m above the throwing point. How fast was the ball thrown?

Homework Equations


xcos30
ysin30

The Attempt at a Solution


Im not sure what I am supposed to do considering there is no velocity given
 

Answers and Replies

  • #2
2,792
592
Im not sure what I am supposed to do considering there is no velocity given
How fast was the ball thrown?
Well, the problem is asking for the initial velocity, so its very natural that the initial velocity is not given to you!!!

Just take a look at the equations you have at hand and see which one has only one unknown, taking into account the data given in the problem.
 
  • #3
311
23
So the ledge coincides with the apex of the parabola
You also need the value for g (gravitational acceleration)
Youll be working on the vertical vector of the launch velocity first
 
  • #4
gneill
Mentor
20,901
2,854
So the ledge coincides with the apex of the parabola
Not necessarily. The projectile can land at the given spot after passing through its zenith.

Fig1.gif
 
  • #5
nasu
Gold Member
3,769
428
So the ledge coincides with the apex of the parabola
You also need the value for g (gravitational acceleration)
Youll be working on the vertical vector of the launch velocity first
This assumption is not implied by the text and is not necessary.
 
  • #6
311
23
Beyond me, sorry.
Dean
 

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