How to calculate projectile off cliff when angle is below th

In summary, the problem involves a stone being thrown downwards from a 50 m tall cliff with an initial velocity of 12 m/s and 22 degrees below the horizontal. The goal is to calculate the time it will take for the stone to hit the ground. The equations used include V=d/t and D=Vi t + 1/2at^2. However, the solution provided does not yield the correct answer of 2.77 seconds and it is unclear how to achieve this answer. It is also important to note that the stone is not thrown horizontally, as indicated by the given information of an initial velocity of 12 m/s and 22 degrees below the horizontal.
  • #1
Abcdefghijk

Homework Statement


Cliff is 50 m tall
Stone thrown downwards with velocity of 12 m/s and 22 degrees below horizontal
What is the time it will take to hit the ground?


Homework Equations


V=d/t
D= Vi t + 1/2at^2

The Attempt at a Solution


Vx1= cos (22)(12)
= +11.12620625
Vy1= sin (22) (12)
= -4.495279121

I solved the triangle (hyp=12) but from here I am not sure what to do. Here is what I attempted from here:

Vertical
(Vi= 0 m/s, a (g)= -9.81 m/s^2, d= 50 m)
d= Vi t + 1/2at^2
t (re-arranged) = square root of d/(1/2a)
t= 10. 1936792 s

Horizontal
(V= 12 m/s, t= 10.1936792 s)
v= d/t
d= vt
d= (12)(10...)
d= 122.324159 m

The correct answer is 2.77 seconds, but I am unable to get this answer and comprehend how to achieve this answer. I would greatly appreciate a walkthrough/explanation of this question and if the angle was above the horizontal as well.

Thanks

 
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  • #2
Abcdefghijk said:
d= Vi t + 1/2at^2
t (re-arranged) = square root of d/(1/2a)
t= 10. 1936792 s
What happened to vi t? Isn't there a downward initial velocity component?
 
  • #3
For the vertical component, the initial velocity should be 0 m/s since the movement is horizontal. Therefore I think that you can eliminate Vi t as it will yield 0.
 
  • #4
Abcdefghijk said:
Stone thrown downwards with velocity of 12 m/s and 22 degrees below horizontal
This means what is says. The stone is not shot horizontally. In fact you calculated its vertical component here
Abcdefghijk said:
Vy1= sin (22) (12)
= -4.495279121
What do you think Vy1 is?
 
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Likes CWatters

What is a projectile?

A projectile is an object that is thrown or launched into the air and then follows a curved path due to the force of gravity acting on it.

How do you calculate the trajectory of a projectile?

The trajectory of a projectile can be calculated using the equations of motion, which take into account the initial velocity, angle of launch, and acceleration due to gravity. These equations can be solved to determine the horizontal and vertical positions of the projectile at any given time.

What is the angle of launch?

The angle of launch is the angle at which the projectile is thrown or launched into the air relative to the horizontal. It is measured in degrees or radians.

What is the maximum height of a projectile?

The maximum height of a projectile is the highest point it reaches in its trajectory. This can be calculated using the equation h = (v^2 * sin^2(angle)) / (2 * g), where v is the initial velocity, angle is the angle of launch, and g is the acceleration due to gravity.

How does changing the angle of launch affect the trajectory of a projectile?

Changing the angle of launch can greatly affect the trajectory of a projectile. A lower angle will result in a shorter and flatter trajectory, while a higher angle will result in a longer and higher trajectory. The optimal angle for maximum distance is 45 degrees.

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