# Maximum acceleration of a Porsche on a concrete surface?

#### philo51

A Porsche 944 Turbo has a rated power of 217 hp and a mass, with the driver, of 1460 kg. Two-thirds of the car's weight is over the drive wheels.

What is the maximum acceleration of the Porsche on a concrete surface where static friction=1.0

1hp=476watts
217hp=103292 watts

and power= Force*velo but whats the force?

What is the speed of the Porsche at maximum power output
thats easy if i get the force i just solve for v

If the Porsche accelerates at , how long does it take until it reaches the maximum power output?
again easy if i can get the first part. any help is appreciated

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#### Doc Al

Mentor
The force acting on the car is the static friction of the road on the tires. The maximum possible static friction force is given by $\mu N$, where N is the normal force pressing the surfaces together. That should get you going.

#### philo51

yea i think i got that but im not sure if the rest is right then

u*N=ma

(1.0*1460kg*9.81)/1460 = a? that doesnt seem right is there another force?

#### Doc Al

Mentor
Friction is the only horizontal force you need worry about. (I presume you may ignore air resistance.) But note that you were told "Two-thirds of the car's weight is over the drive wheels". How would that modify the normal force used to calculate the friction?

#### philo51

ooo right so

1*9.81*(2/3)m=m(total)*a ok that should workk thanks!

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