F=MA + Average Acceleration etc.

[balllla]

Homework Statement

A. A Volkswagen Rabbit has a mass of 1090 Kg and can go from 0mi/hour to 65 mi/hour in 12.0 seconds with an average acceleartion of 2.42 m/s^2. Disregarding friction, what force must the engine be producing?

B.
Disregarding friction, how much mass would need to be removed from the car above if it were to make the same velocity change in only 10.0 seconds with an average acceleration of 2.90m/s^2.

Homework Equations

f=ma

The Attempt at a Solution

a.f=ma
f=(1090 kg) (2.42m/s^2)
f=2640N

okay I get a but do not understand B. How can the average acceleration be 2.42 m/s^2 when 0mi/hr to 65 mi/hour in 12.0 seconds when it is actually 5.41 m/s^2. Help is needed in finishing the problem then...

thank you.

 

[Oddbio]

In part B you are going to use the force you found in part A, NOT the acceleration.
So if you have the same force, but less mass do you think the car can get up to the same speed in more or less time?

 

[GRB 080319B]

okay I get a but do not understand B. How can the average acceleration be 2.42 m/s^2 when 0mi/hr to 65 mi/hour in 12.0 seconds when it is actually 5.41 m/s^2. Help is needed in finishing the problem then...

65 mi/hr = 29 m/s

B.
F = 2640 N
a = 2.90 m/s^2
F = ma

Solve for m. This is the mass of the car after some of the original total mass had been removed. Subtract this mass from m = 1090kg