1) A sports car accelerates from rest to 100 km/h in 6.1 s. What is its average

Question

1) A sports car accelerates from rest to 100 km/h in 6.1 s. What is its average acceleration in m/s2?

m/s2

2)A sports car moving at constant speed travels 100 m in 4.9 s. If it then brakes and comes to a stop in 4.0 s, what is its acceleration? Express the answer in terms of g's, where g = 9.80 m/s2. (Take the positive direction to be the direction of travel.)

g

3)A car slows down from 16 m/s to rest in a distance of 84 m. What was its acceleration, assumed constant?

m/s2

4)A car slows down uniformly from a speed of 20.0 m/s to rest in 6.00 s. How far did it travel in that time?

m

Explanation / Answer

1) initial speed , u = 0 m/s

final speed , v = 100 km/hr

v = 27.8 m/s

average acceleration = (v - u)/t

average acceleration = (27.8 - 0)/6.1

average acceleration = 4.55 m/s^2

2)

contant speed , u = distance/time

u = 100/4.9 m/s

u = 20.41 m/s

let the acceleration is a

Using first equation of motion

v = u + a * t

0 = 20.41 + a * 4.9

a = - 4.16 m/s^2

the acceleration of the car is -4.16 m/s^2

3)

let the acceleration is a

Using third equation of motion

v^2 - u^2 = 2 * a * d

0 - 16^2 = 2 * a * 84

a = -1.52 m/s^2

the acceleration is -1.52 m/s^2

4)

let the acceleration is a

using first equation of motion

v= u + a * t

0 = 20 +a * 6

a = -3.33 m/s^2

Using third equation of motion

v^2 - u^2 = 2 * a * d

0 - 20^2 = -2 * 3.33 * d

d = 60 m

the distance travelled in stopping is 60 m

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