Getting work out of kinetic energy

In summary, the conversation revolves around the presenter's attempt to demonstrate the concept of kinetic energy in a presentation on energy. They have tried using a pinewood derby car to supply a constant force and measuring its impact on a suspended mass, but have encountered difficulties with energy transfer. Suggestions such as using a ballistic pendulum or observing the extension of a spring attached to the car while in motion are given to improve the demonstration.
  • #1
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I am doing a presentation on energy as part of a class project.As part of the presentation I would like to physically demonstrate that the amount of work you can get out of a moving body (its kinetic energy) is equal to the amount of work you put in.I want to somehow take a moving body and get it to do a measurable amount of work that would be equal to its kinetic energy.This is turning out to be surprisingly difficult.I rigged a pinewood derby car so that I could supply a constant force over some set amount of distance.I tried running the car into a mass suspended on the end of the string and seeing how high the mass rose as a result but not all of the energy is being transferred to the mass (the car still has some velocity after impact).??Any suggestions would be greatly appreciated.
 
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  • #2
Make sure that you get a plastic impact by having the car captured in your ballistic pendulum. Then you will have to account for the loss due to impact.
 
  • #3
Use a Newtons cradle.
 
  • #4
Hook a (weakish) spring on to the car as it's moving. Observe the maximum extension, x, (preferably by taking a rapid succession of pictures). Hope to find that
[tex]\frac{1}{2}mv^2 = \frac{1}{2}kx^2.[/tex]
Negligible energy dissipated in collision.
 
  • #5


Hello,

Firstly, I commend you on your project and your desire to physically demonstrate the concept of kinetic energy. It is indeed a challenging task, but I believe with some adjustments, you can achieve your goal.

One suggestion would be to use an inclined plane set at a specific angle with a stopper at the end. You can release the pinewood derby car from the top of the inclined plane, and it will roll down until it hits the stopper, transferring all its kinetic energy into the stopper. The height at which the stopper rises can be measured and can be used to calculate the amount of work done, which should be equal to the initial kinetic energy of the car.

Another option could be to use a pulley system where the pinewood derby car is attached to one side of the pulley, and a weight is attached to the other side. As the car moves, it will lift the weight, and the height to which the weight is lifted can again be used to calculate the work done, which should be equal to the kinetic energy of the car.

I hope these suggestions are helpful and wish you all the best for your presentation.

Best regards,
 

1. What is kinetic energy?

Kinetic energy is the energy an object possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its current velocity.

2. How is kinetic energy calculated?

Kinetic energy is calculated using the formula KE = 1/2 * m * v^2, where m is the mass of the object and v is its velocity.

3. What are some examples of kinetic energy?

Some examples of kinetic energy include a moving car, a swinging pendulum, a flying airplane, and a rolling ball.

4. How can kinetic energy be used to do work?

Kinetic energy can be used to do work by transferring its energy to other objects. For example, a moving car can transfer its kinetic energy to the brakes to stop, or a falling object can transfer its kinetic energy to a turbine to generate electricity.

5. What factors affect the amount of kinetic energy an object has?

The amount of kinetic energy an object has is affected by its mass and velocity. The greater the mass and velocity of an object, the greater its kinetic energy will be.

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