Solving a Ball Thrown off a Cliff: How Long Does it Take?

  • Thread starter NotInMrPutmansClass
  • Start date
  • Tags Tags
    Ball
4 replies · 3K views · last reply
NotInMrPutmansClass
Messages
5
Reaction score
0
Homework Statement
Find the height of a cliff using a ball thrown at an angle and find how long it takes the ball to hit the ground.
Relevant Equations
a-sinA, aCosA
This is the question:
A ball is thrown with a speed of 6m/s at an angle of 25° above the horizontal from the top of a cliff. The ball strikes the ground 15 m from the bottom of the cliff.

How long does it take the ball to strike the ground?

How long is the cliff?Here's a visual representation of the problem.
Handwritten sketch of a projectile launched from a cliff edge at 6 m/s and 25 degrees above horizontal, with a curved trajectory landing 15 m from the cliff base. Labels read height of the cliff = ? and time = ?.

I broke the angle into vectors
Handwritten right triangle with a 6 m/s hypotenuse at 25° to the horizontal. Labels: 6Sin25° = 2.5357 m/s (vertical) and 6Cos25° = 5.4378 m/s (horizontal).


I solved for the time of the ball in the
x-axis

t=d/v
t=15m / 5.4378m/s
t = 2.7584 Seconds

But now I'm stuck and I'm lost on what to do next
 
Last edited:
Welcome to PF.

I'm not able to see much in your attached images -- I seem to only be seeing thumbnail-size images and they are not well lit. Could you maybe use a printer/scanner to generate better copies?
 
NotInMrPutmansClass said:
But now I'm stuck and I'm lost on what to do next
After you post legible figures, you should write the appropriate equation(s) for the motion in the vertical direction.
 
berkeman said:
Welcome to PF.

I'm not able to see much in your attached images -- I seem to only be seeing thumbnail-size images and they are not well lit. Could you maybe use a printer/scanner to generate better copies?
I reposted the pictures and they seem to be fine now.
 
NotInMrPutmansClass said:
I reposted the pictures and they seem to be fine now.
What's the problem with getting the height of the cliff, now you have the time of flight?