Projectile Motion Ball off Cliff Help

In summary, the conversation discusses finding the initial velocity and angle of launch of a golf ball hit from a cliff top. The given variables are the height of the cliff (46 m), the distance traveled by the ball (154 m), and the time it takes to reach the ocean (7.0 s). The person is unsure of how to approach the problem but attempts to use two-dimensional kinematic equations. However, their answer does not match the instructor's.
  • #1
caels
5
0
I missed a few days of class and have a quiz tomorrow so I'm not entirely sure where to start with this. The question is:

A golfer hits a ball (m = 38 g) from a cliff top (h = 46 m) and times how long it takes to splash in the ocean (t = 7.0 s). The ball hits the water at a distance (x = 154 m) from the vertical cliff bottom. Find the ball's initial velocity and the angle of launch.

I have y = 46 m, x = 154 m, t = 7.0 s

I assume I have to use the two-dimensional kinematic equations, but I just can't seem to get anywhere towards finding the initial velocity.

My first thought was

x = v_0x * t

v_0x = 154 / 7 = 22 m/s

Then take

y = (v_0y)t+1/2 gt^2 = 7(v_0y) - 240.34

v_0y = 40.905

And then square both of those and take the square root. But the answer I get doesn't agree with the instructors, so I'm lost.
 
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  • #2
You did not use the cliff height in the second equation.
 

1. What is projectile motion?

Projectile motion is the motion of an object in a two-dimensional plane under the influence of gravity. It is a type of motion where an object moves through the air, following a curved path due to the combination of its initial velocity and the force of gravity.

2. How does the height of a cliff affect the motion of a ball thrown off it?

The height of the cliff affects the initial velocity of the ball, which in turn affects the time it takes for the ball to reach the ground and the distance it travels. The higher the cliff, the longer the ball will take to reach the ground and the farther it will travel.

3. What factors affect the trajectory of a projectile?

The trajectory of a projectile is affected by its initial velocity, the angle at which it is thrown, and any external forces acting on it such as air resistance or wind.

4. How do you calculate the final velocity of a ball thrown off a cliff?

The final velocity of a ball thrown off a cliff can be calculated using the equation v = u + at, where v is the final velocity, u is the initial velocity, a is the acceleration due to gravity, and t is the time it takes for the ball to reach the ground.

5. What is the difference between horizontal and vertical components of projectile motion?

The horizontal component of projectile motion refers to the motion of the object in the x-direction, while the vertical component refers to the motion in the y-direction. The horizontal component remains constant, while the vertical component is affected by the force of gravity.

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