4-When you see a traffic light turn red, you apply the brakes until you come to

Question

4-When you see a traffic light turn red, you apply the brakes until you come to a stop. Suppose your initial speed was 11.9 m/s, and you come to rest in 34.1 m. How much time does this take? Assume constant deceleration.

5-

A cheetah can accelerate from rest to 26.0 m/s in 6.26 s.
(a) Assuming constant acceleration, how far has the cheetah run in this
time?

(b) After sprinting for just 3.13 s, is the cheetah's speed 13.0 m/s, more
than 13.0 m/s, or less than 13.0 m/s?
(c) What is the cheetah's average speed for the first 3.13 s of its sprint?

For the second 3.13 s of its sprint?

(d) Calculate the distance covered by the cheetah in the first 3.13 s and the
second 3.13 s.
first 3.13 s
second 3.13 s

Please solve them in detail

Explanation / Answer

4)

initial speed , u = 11.9 m/s

distance , d = 34.1 m

final speed , v = 0 m/s

let the constant deceleration is a

Using third equation of motion

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

0 - 11.9^2 = 2 * a * 34.1

a = - 2.08 m/s^2

Now, using first equation of motion

v = u + at

0 = 11.9 - 2.08 * t

t = 5.73 s

the time taken to stop is 5.73 s

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