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Who can answer a Physics question

[From: ] [author: ] [Date: 11-06-10] [Hit: ]
I find this.http://bufen.......
An advertisement states that a 1,250kg car can go from 0 to 60 miles per hour in 3.75 seconds.
-Determine its acceleration
-Calculate net force required to give the car the acceleration
-Find the normal force exerted by the road on the car
- The coefficient of friction of the car tires is .80
Calculate the maximum force of friction between the car tires and the road
- Explain if the advertisement is possible

-
60 miles/h = 26.67 m/s

a = delta(v)/delta(t) = (26m/s) / (3.75 s) = 7.11 m/s^2

F = m a = 1250 kg * 7.11 m/s^2 = 8888.9 N

Normal force equals the weight of the car:

Fn = m g = 1250 kg * 9.81 m/s^2= 11263 N

Max friction equals
F_fricmax = mu * Fn = 0.80 * 11263 N = 9810 N

So the advertisement is possible, but only just. The maximal frictional force is just enough to deliver the force needed for accelerating at 7.11 m/s^2 .

(A quicker check would be that 7.11 m/s^2 is less than 0.80 g , because the mass drops out of the equation.)

-
It's amazing!I find this.http://bufen.info/62941/cars-tyres
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