Work-Kinetic Energy Theorem

In summary, the high diver with a mass of 62kg walks off a 15 meter platform with an initial velocity of 0 and reaches a depth of 2.2 meters in the pool before coming to a stop. The change in kinetic energy is -9114J and the average force of the water pushing up on her is 4750N, corresponding to about 8 g's of acceleration. To find these values, the work energy theorem is applied and the KE of the diver when she hits the water is used to calculate the change in kinetic energy. Another force acting on the diver is the buoyant force of the water, which is equal to the average force of the water pushing up on her.
  • #1
master_333
25
0

Homework Statement


A high diver(m = 62kg) walks off a platform 15 meters above the water below (assume velocity inital = 0). The diver reaches a depth of 2.2 metres in the pool before coming to a stop.
1. What is the diver's change in kinetic energy (Answer: -9114J)
2. What is the average force of the water pushing up on her? (Answer: 4750 N ... the acceleration corresponds to a about 8 g's)

I don't get the correct answer to the first question and I don' know how to attempt the second question. Please help and please show me the steps.

Homework Equations


Work Energy Theorem

The Attempt at a Solution


1. Change in GPE = Change in KE
mgh = change in KE
(62kg)(9.8)(17.2m(
change in KE = 10450.72, which is the wrong answer.
 
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  • #2
master_333 said:
1. What is the diver's change in kinetic energy
I presume they want the change in KE once she hits the water. So what is her KE when she hits the water?
 
  • #3
Doc Al said:
I presume they want the change in KE once she hits the water. So what is her KE when she hits the water?
The KE when she hits the water is 9114J
 
  • #4
master_333 said:
The KE when she hits the water is 9114J
There you go. So you can answer part 1 now, correct?
 
  • #5
How do I sart part 2
 
  • #6
master_333 said:
How do I sart part 2
Sorry, How do I start part 2
 
  • #7
master_333 said:
Sorry, How do I start part 2
By applying the work energy theorem.

Remember, you are trying to find the average force that the water exerts. What other force acts?
 

1. What is the Work-Kinetic Energy Theorem?

The Work-Kinetic Energy Theorem is a physics principle that states the work done on an object is equal to the change in its kinetic energy. It is often used to analyze the motion of objects and their energy transformations.

2. How is the Work-Kinetic Energy Theorem derived?

The Work-Kinetic Energy Theorem is derived from the laws of motion and the definition of work. It can be mathematically expressed as W = ΔKE = ½mv2f - ½mv2i, where W is work, ΔKE is change in kinetic energy, m is mass, vf is final velocity, and vi is initial velocity.

3. How is the Work-Kinetic Energy Theorem applied in real-life situations?

The Work-Kinetic Energy Theorem has many practical applications, such as in the design of roller coasters and other amusement park rides, analyzing the motion of vehicles, and understanding the behavior of moving objects in different environments.

4. Can the Work-Kinetic Energy Theorem be used for all types of motion?

Yes, the Work-Kinetic Energy Theorem can be applied to all types of motion, including linear, rotational, and oscillatory motion. However, it is most commonly used for analyzing linear motion.

5. What are the limitations of the Work-Kinetic Energy Theorem?

The Work-Kinetic Energy Theorem assumes that there are no external forces acting on the object and that the object has a constant mass. It also does not take into account other forms of energy, such as potential energy, which may affect the overall energy of the system. Therefore, it may not accurately describe the motion of all objects in all situations.

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