Question

Directions: Consider a 2-kg bowling ball sits on top of a building that is 40 meters tall. It falls to the ground. Think about the amounts of potential and kinetic energy the bowling ball has:
• as it sits on top of a building that is 40 meters tall.
• as it is half way through a fall off a building that is 40 meters tall and travelling 19.8 meters per second.
as it is just about to hit the ground from a fall off a building that is 40 meters tall and travelling 28 meters per second.

1. Does the bowling ball have more potential energy or kinetic energy as it sit on top of the building? Why?
Answer:
(Score for Question 2: ___ of 7 points)
2. Does the bowling ball have more potential energy or kinetic energy as it is half way through its fall? Why?
Answer:
(Score for Question 3: ___ of 7 points)
3. Does the bowling ball have more potential energy or kinetic energy just before it hits the ground? Why?
Answer:
(Score for Question 4: ___ of 4 points)
4. What is the potential energy of the bowling ball as it sits on top of the building?
Answer:
(Score for Question 5: ___ of 4 points)
5. What is the potential energy of the ball as it is half way through the fall, 20 meters high?
Answer:
(Score for Question 6: ___ of 3 points)
6. What is the kinetic energy of the ball as it is half way through the fall?
Answer:
(Score for Question 7: ___ of 3 points)
7. What is the kinetic energy of the ball just before it hits the ground?
Answer:

Answer 1

1. The bowling ball have more potential energy as it sit on top of the building

2.The bowling ball have same potential energy and kinetic energy as it is half way through its fall

3. The bowling ball have more kinetic energy just before it hits the ground

4. The potential energy of the bowling ball as it sits on top of the building is 784J

5. The potential energy of the ball as it is half way through the fall, 20 meters high is 392J

6. The kinetic energy of the ball as it is half way through the fall is 392J

7. The kinetic energy of the ball just before it hits the ground is 784J

Explanation:

Calculating potential energy and kinetic energy for all the instances,

1. ball on top of a 40 meters tall building

Potential energy at the top of building with a height of 40m = mgh

P.E = mgh =2*9.8*40= 784J

At the top pf the building since v=0 kinetic energy is zero

2. half way through a fall off a building that is 40 meters tall and travelling 19.8 meters per second

Potential energy when it is half way through fall = mgH

where H represents new height that is equal to 20m

hence P.E=mgH=2*9.8*20= 392J

Kinetic energy  of the ball is $\frac{1}{2} mv^{2} = \frac{1}{2} *2*19.8^{2}$=392.04J

3.  Just about to hit the ground from a fall off a building that is 40 meters tall and travelling 28 meters per second.

The potential energy of ball just before it hits the ground = mgh= 2*9.8*0=0J

kinetic energy =$\frac{1}{2} mv^{2}$= 784J