A car’s velocity as a function of time is given by vx(t) = - t 2 , where =3.00m/

Question

A car’s velocity as a function of time is given by vx(t) = - t 2 , where =3.00m/s and =0.100m/s3 . Assume the car’s initial position is 0m. Which of the following statements is false? a.) The car’s position at t=5s is +10.83m. b.) When the car reaches x=10.95m, it reverses course and moves in the negative direction. c.) The car’s average velocity over the first 5s of motion is +1.75m/s. d.) The car’s average acceleration over the first 5s of motion is -0.5m/s2 . e.) The car’s acceleration at t=5s is -1.0m/s2 .

Explanation / Answer

a)

vx(t) = - t^2

vx(t) = 3 - 0.100*5^2

vx(t) = 3 - 2.5 = 0.5 m/s

x = vt = 0.5 x 5 = 2.5 m

Ans : false

b) True

c) vx(t) = 3 - 2.5 = 0.5 m/s

Ans : false

d)

vx(t) = - t^2

a(t) = -2t = -2 x 0.100 x 5 = -1 m/s^2

average acceleration = -1 m/s^2 / 2 = -0.5 m/s^2

Ans = true

e) a(t) = -2t = -2 x 0.100 x 5 = -1 m/s^2

Ans :- True

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