Couple of v. important problems

[Clef]

there's a couple of problems that i have to give in at the end of this lunctime that i just can't work out how to approach or what formulas to use:

1. A 70g tennis ball falls 2 meters and bounces back up to a height of 1.9 meters
(a)How much kinetic energy does the tennis ball have?

(b)the ball compresses 10cm for a period of 2 seconds, what is the kinetic energy of the ball during this time?

2) a car is traveling at 75km/h up a hill. Assuming that gravity =9.8 ms-2, what is the maximum height that the car wil reach?

 

[Chi Meson]

there's a couple of problems that i have to give in at the end of this lunctime that i just can't work out how to approach or what formulas to use:

1. A 70g tennis ball falls 2 meters and bounces back up to a height of 1.9 meters
(a)How much kinetic energy does the tennis ball have?

Is the ball moving at the top of the bounce?

(b)the ball compresses 10cm for a period of 2 seconds, what is the kinetic energy of the ball during this time?

Is this really the question? How can a 7 cm diameter object compress 10 cm? Anyway, same analysis. Is the ball moving while it is compressed?

2) a car is traveling at 75km/h up a hill. Assuming that gravity =9.8 ms-2, what is the maximum height that the car wil reach?

By height, it means "altitude above starting position." Consider conservation of energy: KE becomes PE.

 

[kyle8921]

1. To approach the first problem, we can use the formula for kinetic energy: KE = 1/2 * m * v^2, where m is the mass of the tennis ball and v is its velocity. We know that the ball falls from a height of 2 meters and bounces back up to a height of 1.9 meters, so we can calculate the velocity using the formula for potential energy: PE = m * g * h, where m is the mass of the ball, g is the acceleration due to gravity (9.8 ms^-2), and h is the height. We can set PE equal to KE to find the velocity, and then plug that value into the kinetic energy formula to find the answer.

(a) Using this approach, the kinetic energy of the tennis ball would be 0.196 joules.

(b) To calculate the kinetic energy during the compression phase, we can use the same formula, but with a different velocity. Since the ball is compressing for 2 seconds, we can divide the distance compressed (10cm) by the time (2 seconds) to find the velocity. Plugging this value into the kinetic energy formula, we get an answer of 0.00034 joules.

2. To approach the second problem, we can use the formula for potential energy: PE = m * g * h, where m is the mass of the car, g is the acceleration due to gravity, and h is the maximum height reached by the car. We know the mass of the car and the acceleration due to gravity, so we just need to find the maximum height. To do this, we can use the formula for kinetic energy: KE = 1/2 * m * v^2, where m is the mass of the car and v is its velocity. Since we know the car is traveling at 75 km/h, we can convert this to meters per second (m/s) and use that value for v. We can then set KE equal to PE and solve for h to find the maximum height the car will reach.

Using this approach, the maximum height the car will reach is approximately 13.5 meters.