How Fast Does a Flywheel Spin in a Stopping Hybrid Car?

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In summary, the conversation discusses the use of a flywheel in a hybrid vehicle to capture energy during braking and calculates the speed of the flywheel when the car stops in an urban area. It also discusses a downhill cart race and determines the maximum speed attained and the time it takes for the first cart to cross the finish line. There is also a discussion about the speed limit in an urban area and its impact on the calculations.
  • #1
madmike1
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I need a bit of help with a few questions.

In a hybrid vehicle a flywheel is used to capture the energy of the car during braking. If the car has a total mass of 850kg and the flywheel has a mass-moment of inertia equal to 14kgm2 determine the speed of the flywheel when the car stops for traffic lights in an urban area (you may assume 100% efficiency).

and...

A downhill cart race is to start at 10.30 am precisely. The hill has a slope that varies from 1:4 to 1:10 and has a vertical drop of 75m. If the track length is 0.75km (the first 0.5 km being the hill itself) and assuming no energy losses determine
a) the maximum speed attained
b) the time the first cart crosses the finish line

thanks
 
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  • #2
Welcome to PF! What have you attempted so far with these questions. You cannot receive any help until you have made some effort yourself.
 
  • #3
change in kinetic energy of car to rotational energy of flywheel
so would have 0.5MV^2=0.5Iw^2

=> w^2=(M/I)V^2
=> w=7.79V
and then the drop from 30mph to zero needs to be taken into account somehow.

am i right?
 
  • #4
and then the drop from 30mph to zero needs to be taken into account somehow.
Yes - the change in kinetic energy based on the velocity decreasing from 30 mph to 0 goes into the flywell, which increases it rotational kinetic energy.

BTW, the 30 mph is not mentioned in the OP. This is necessary piece of information in this problem.
 
  • #5
it mentions that it is in an urban area so i assumed that the speed limit would be 30 therefore the speed of the car would be 30?? i don't know though
 
  • #6
madmike1 said:
it mentions that it is in an urban area so i assumed that the speed limit would be 30 therefore the speed of the car would be 30?? i don't know though

Yes, if you're in the Uk then the speed limit will be 30mph for the urban area. You can then work out the change in kinetic energy.
 
  • #7
would the maximum speed attained down the hill be 38.36m/s?
using v=sqrt2gh?
or is velocity not the same as maximum speed?
 
  • #8


Could anyone confirm if this is correct, including the thread starter?

Thanks
 

Related to How Fast Does a Flywheel Spin in a Stopping Hybrid Car?

1. What is a flywheel breaking problem?

The flywheel breaking problem is a common issue in mechanical systems, where the flywheel, which is responsible for storing rotational energy, fails to operate properly due to excessive wear and tear, imbalance, or other factors. This can lead to the flywheel breaking or malfunctioning, causing the entire system to fail.

2. How does a flywheel breaking problem occur?

A flywheel breaking problem can occur due to various reasons such as inadequate maintenance, excessive load on the system, poor quality materials, or manufacturing defects. It can also happen if the system is not designed to handle the required amount of energy or if the flywheel is not properly balanced.

3. What are the signs of a flywheel breaking problem?

Some common signs of a flywheel breaking problem include strange noises or vibrations coming from the system, difficulty in starting the system, or the system not performing at its optimal level. In some cases, the flywheel may also break or shatter completely, causing the system to stop working.

4. How can a flywheel breaking problem be prevented?

To prevent a flywheel breaking problem, regular maintenance and proper handling of the system are crucial. The flywheel should be balanced correctly, and the system should be designed to handle the required amount of energy. It is also essential to use high-quality materials and perform regular inspections to identify any potential issues before they become more significant problems.

5. Can a flywheel breaking problem be fixed?

In most cases, a flywheel breaking problem can be fixed by replacing the damaged flywheel with a new one. However, depending on the severity of the issue, other components of the system may also need to be repaired or replaced. It is crucial to address the problem as soon as possible to prevent further damage to the system.

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