Projectile's final velocity

In summary, the conversation discusses finding the velocity of a rock thrown from a 50m cliff with an initial velocity of 7m/s and an angle of 53 degrees. The equations used are vfy=sin(theta)*vi-gt and vf^2=(vi*sin(theta))^2-2gy. The attempt at a solution includes using x to represent two different quantities and attempting to find the velocity by plugging in x into the second equation, but not obtaining the correct answer. The time of flight is also considered, but it is unclear why it is given by the second equation.
  • #1
vinamas
43
1

Homework Statement


A rock is thrown from a cliff that is 50m long with an initial velocity of 7m/s and an angle of 53, find the rock's veloctity before it hits the ground

Homework Equations


vfy=sin(theta)*vi-gt
vf^2=(vi*sin(theta))^2-2gy

The Attempt at a Solution


x=vi*cos()t
t=x/(vi*cos)
x=7*cos(53)-2*9.81*(x/(vi*cos(53)))^2
x =2.49 or x=-6.11
at this point i tried to plug in x into vf^2=(vicos)^2-2gy
but none of them give 32 m/s which is the answer according to the answer's sheet
 
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  • #2
Some questions for you to consider:
In your solution what is x? It appears you are using x to represent two different quantities.
Why do you think the time of flight is given by your second equation?
 

1. What is the equation for calculating the final velocity of a projectile?

The equation for calculating the final velocity of a projectile is Vf = Vi + at, where Vf is the final velocity, Vi is the initial velocity, a is the acceleration, and t is the time.

2. How does the angle of projection affect the final velocity of a projectile?

The angle of projection can affect the final velocity of a projectile by changing the vertical and horizontal components of the initial velocity. A higher angle of projection will result in a higher vertical velocity component, while a lower angle of projection will result in a lower vertical velocity component. The horizontal velocity component remains constant.

3. Does the mass of the projectile affect its final velocity?

The mass of the projectile does not directly affect its final velocity. However, a heavier projectile may have a greater resistance to air resistance, resulting in a slightly higher final velocity. This effect is usually negligible for most practical situations.

4. How does air resistance impact the final velocity of a projectile?

Air resistance can decrease the final velocity of a projectile by exerting a force in the opposite direction of the projectile's motion. This force is dependent on the shape and size of the projectile, as well as the density of the air and the velocity of the projectile.

5. Can the final velocity of a projectile ever be greater than the initial velocity?

Yes, the final velocity of a projectile can be greater than the initial velocity if there is a significant force acting on the projectile in the direction of its motion. This is known as a propelling force and can occur in situations such as a rocket launch or a ball being kicked by a player.

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