Power Needed to Accelerate 1200 kg Car from Rest to 20 m/s

In summary, the conversation revolves around finding the average power required for a car with a mass of 1200 kg to accelerate from rest to a velocity of 20 m/s in 6.0 seconds. After discussing the formula for average power and calculating the kinetic energy of the car, it is determined that the average power required is 40 kW. This aligns with option D as the correct answer.
  • #1
wolves5
52
0
A car with a mass of 1200 kg accelerates from rest to 20 m/s in 6.0 seconds. What average power must the car produce to cause this acceleration?

a. 5 kW
b. 15 kW
c. 30 kW
d. 40 kW

For this problem, I did (1200)(9.81) and got the force. Then I used d= (6 seconds) x ((0 +20)/2) to find the distance. I got 60 meters as my distance. I then did force times distance to get the Work. Then I divided the Work by 6 seconds because that's how you get power. I got an answer that was none of the options above. What am I doing wrong?
 
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  • #2
The weight of the car is not the force doing the acceleration (unless of course it's fallen off a cliff!).

The work done while accelerating the car goes into giving it kinetic energy, expressed as velocity. If you know the velocity at the end of 6.0 seconds you should be able to calculate the work done; what's the kinetic energy for mass 1200kg moving with velocity 20 m/s?
 
  • #3
The kinetic energy is 240000 J.
 
  • #4
Do you divide 240,000 by 6 seconds? I got 40,000 Watts when I did that which is 40 kW. So is it D?
 
  • #5
wolves5 said:
Do you divide 240,000 by 6 seconds? I got 40,000 Watts when I did that which is 40 kW. So is it D?

You've already stated that average power is given by work done divided by the time over which it is done. So you should have confidence in your result.
 
  • #6
So the kinetic energy or the 240,000 J was the Work?
 

Related to Power Needed to Accelerate 1200 kg Car from Rest to 20 m/s

1. What is the formula for calculating power?

The formula for calculating power is power = work/time. This means that power is equal to the amount of work done divided by the time it takes to do that work.

2. How do you calculate the work done on a car?

To calculate the work done on a car, you need to know the force applied and the distance traveled. The formula for work is work = force x distance. This means that the amount of work done is equal to the force applied multiplied by the distance traveled.

3. How do you calculate the force needed to accelerate a car?

The force needed to accelerate a car can be calculated using Newton's second law of motion, which states that force = mass x acceleration. In this case, the mass of the car is 1200 kg and the acceleration is 20 m/s2. This means that the force needed to accelerate the car is 24,000 N.

4. What is the unit of power?

The unit of power is watts (W) in the International System of Units (SI). However, power can also be measured in horsepower (hp) or kilowatts (kW).

5. How long does it take to accelerate the car to 20 m/s?

To calculate the time it takes to accelerate the car to 20 m/s, you can use the formula time = velocity/acceleration. In this case, the velocity is 20 m/s and the acceleration is 20 m/s2. This means that it takes 1 second to accelerate the car to 20 m/s.

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