Engine power and car acceleration

In summary: So if an engine has a power of 350 watts, and it takes 4.3 seconds to reach 100 km/h, the fraction for that speed would be 0.7.
  • #1
linnus
23
0

Homework Statement


The Porsche® 911 GT3 has a 380 hp engine and a mass of 1.4×103 kg. The car can accelerate from 0 to 100 km/h in 4.3 seconds. What percentage of the power supplied by the engine goes into making the car move? Assume that the car's acceleration is constant and that there are 746 Watts/hp.


Homework Equations


p=w/t
k=1/2mv^2
a=v/t

The Attempt at a Solution



Not sure...
 
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  • #2
Power of engine in Watts?

Energy to accelerate 1.4×10^3 kg from 0 to 100 km/h?

Power to do that in 4.3 seconds?
 
  • #3
What will the kinetic energy of the car be at 100 km/h?

Power is change of energy per change in time. You calculate change in energy and you are given change in time.
 
  • #4
so you would do
power that it uses for it to reach its final velocity/total power right?
 
  • #5
Actually its a stupid question. Or maybe a trick question.

"What percentage of the power supplied by the engine goes into making the car move?" Trivially: we have no information about losses -- services such as airco, electrical power, servo etc and frictional losses -- so must assume these are zero. A growed up question would not simply ignore those. More seriously we have no information about how much power the engine supplies, only about the max it can supply. Maybe, just maybe, it wasn't running at max power RPM with the throttle mashed into the carpet. Ignoring losses ALL the power the engine supplies goes into making it move. Where else would it go?

"An airplane crashes on the border of USA and Canada. Where do they bury the survivors?"

"Have you stopped beating your wife yet?"
 
  • #6
You find the power that it took to reach that speed. Actually, you find the ENERGY it took to reach that speed, then divide it by the time it took to reach that speed to get power.

Then you divide that my the engine's power to get a fractional part.
 

1. What is engine power and how does it affect car acceleration?

Engine power is the measure of the amount of work an engine can do in a certain amount of time. It is usually measured in horsepower. The higher the engine power, the more force the engine can produce, which results in faster acceleration.

2. How is engine power different from torque?

Engine power and torque are often used interchangeably, but they are not the same. Engine power is the rate at which the engine can do work, while torque is the measure of the engine's twisting force. Both play a role in car acceleration, but in different ways.

3. Does a bigger engine always mean more power and faster acceleration?

Not necessarily. While a bigger engine may have more cylinders and a larger displacement, it does not always equate to more power. Many other factors, such as engine design, turbocharging, and fuel efficiency, also play a role in determining engine power and acceleration.

4. Can you increase engine power and acceleration without modifying the engine?

Yes, there are a few ways to increase engine power and acceleration without making any major modifications to the engine. One way is to reduce the weight of the car, as a lighter car requires less power to accelerate. Another way is to improve the aerodynamics of the car, reducing drag and allowing for faster acceleration.

5. Why do electric cars have instant acceleration?

Electric cars have instant acceleration because they use electric motors instead of traditional combustion engines. Electric motors can deliver maximum torque instantly, resulting in quick acceleration. Additionally, electric cars do not have gears like traditional cars, allowing for a smoother and more continuous power delivery.

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