Acceleration of car and power

In summary: The answer is 121 kWIn summary, the conversation discusses the calculation of the average power of a car with a mass of 1250 kg that accelerates from 0 to 100 km/h in 4 seconds. The correct formula for calculating power is discussed, as well as the importance of using the correct units. The final answer is determined to be 121 kW.
  • #1
thereddevils
438
0

Homework Statement



A car o fmass 1250 kg accelerates from 0 to 100 km/h in 4 s . The average power of the car is ?

Homework Equations





The Attempt at a Solution



Though it looks simple , but i don see my mistake.

The average power is the change in kinetic energy over time ,

(1/2 x 1250 x 100^2)/(4)

is my working correct ? But that doesn't give the answer which is 121 kW
 
Physics news on Phys.org
  • #2


For the formula to yield an answer in watts, you need to convert km/h into m/s. Divide the answer you get by 1000 to get an answer in kW.
 
  • #3


You know the change in velocity and the change in time so you can calculate the acceleration. Knowing the acceleration and time you can calculate the distance the car travels. Knowing the mass of the car and its acceleration you can calculate the force on the car. Knowing the force and distance you can calculate the work done. Power equals work/ change in time.
 
  • #4


RTW69 said:
You know the change in velocity and the change in time so you can calculate the acceleration. Knowing the acceleration and time you can calculate the distance the car travels. Knowing the mass of the car and its acceleration you can calculate the force on the car. Knowing the force and distance you can calculate the work done. Power equals work/ change in time.

This over complicates things quite a bit. The work is given by the difference of kinetic energy. thereddevils only mistake is the usage of the wrong units.
 
  • #5
.

Your working is correct, but you have forgotten to convert the speed from km/h to m/s. The correct equation is:

Average power = (1/2 x 1250 x (100/3.6)^2)/(4) = 121 kW

The mistake was in not converting the speed from km/h to m/s. Remember that 1 km/h = 1000/3600 m/s, so the speed should be (100/3.6) m/s. This conversion is necessary because the mass is given in kilograms and the speed should be in meters per second for the equation to give the correct answer in watts.
 

1. What is the relationship between acceleration and power in a car?

The acceleration of a car is directly proportional to the power output of its engine. This means that the more power an engine produces, the faster the car can accelerate.

2. How does the weight of a car affect its acceleration?

The weight of a car has a significant impact on its acceleration. Heavier cars require more power to achieve the same acceleration as lighter cars. This is because a heavier car has more inertia, meaning it is harder to get it moving.

3. Can a car's acceleration be improved by increasing its power?

Yes, increasing a car's power can improve its acceleration. However, there are other factors that also affect acceleration, such as weight, aerodynamics, and traction. So simply increasing power may not always result in a significant improvement in acceleration.

4. How does the type of transmission affect a car's acceleration?

The type of transmission in a car can greatly impact its acceleration. Cars with manual transmissions generally have more control over gear selection, allowing for quicker acceleration. On the other hand, cars with automatic transmissions may have a smoother acceleration due to the constant power flow.

5. Is there a limit to how fast a car can accelerate?

Yes, there is a limit to how fast a car can accelerate. This is due to physical limitations such as engine power, weight, aerodynamics, and tire traction. Additionally, there are also legal limitations and safety considerations that prevent cars from reaching their maximum acceleration potential.

Similar threads

  • Introductory Physics Homework Help
Replies
20
Views
882
Replies
2
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
1K
  • Introductory Physics Homework Help
Replies
30
Views
2K
  • Introductory Physics Homework Help
Replies
11
Views
2K
  • Introductory Physics Homework Help
2
Replies
48
Views
7K
  • Introductory Physics Homework Help
Replies
15
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
11
Views
627
  • Introductory Physics Homework Help
Replies
12
Views
1K
Back
Top