Question

A Porsche 944 Turbo has a rated engine power of 217 hp . 30% of the power is lost in the drive train, and 70% reaches the wheels. The total mass of the car and driver is 1500 kg , and two-thirds of the weight is over the drive wheels.

Part A

What is the maximum acceleration of the Porsche on a concrete surface where μs=1.00 ?

Express your answer with the appropriate units.

amax =

Part B

If the Porsche accelerates at amax , what is its speed when it reaches maximum power output?

Express your answer with the appropriate units.

v =

Part C

How long does it take the Porsche to reach the maximum power output?

Express your answer with the appropriate units.

t =

Answer 1

Given that , 30% of the power is lost in the drive train, and 70% reaches the wheels.

The total mass = 1520 kg,

and two-thirds of the weight is over the drive wheels

= 1500*2/3 = 1000

217 hp = 161,882 watts
70% = 113,317.4 watts

Now calculating frictional force

Friction force = μs * (weight over drive wheels)
Friction force = 1 *1500*2/3* 9.8 = 9800 N

Part A) Maximum force = mass * maximum acceleration
Maximum acceleration = 9800 / 1500 = 6.5333 m/s^2

part B) Power = Force * speed
113,317.4 = 9800* speed
Speed =11.56 m/s

Part C) Max Acceleration = speed ÷ time
6.5333 = 11.56/time
Time = 1.77 seconds