Question

A old Chevy accelerates at a rate of 3.8 m/s^2. How much time would it take to reach the speed limit of 100 km if the car was travelling at the speed of 70.0 km?

a) 2.9 s
b) 3.7 s <----
c) 5.4 s
d) 30.0 s


2. Find the acceleration of a skier sliding down a mountain at a rate of 32.0 m/s for 10.0 s.

Answer: a = -3.2 m/s^2

Answer 1

I hope the speed is km/s

You will have to convert km/s to m/s

Acceleration=change in velocity/time

Change in velocity/acceleration=time

So,

100km/s -70km/s/3.8m/s=t

t= about 8 s; I don't agree with any of these answers.


2.)

You are correct.

Answer 2

Sorry! The speed is 110 km/h! So sorry! D:

Answer 3

Then the answer should be answer choice A, and not B.

Acceleration=change in velocity/time

Change in velocity/acceleration=time

So,

110km/h=30.56m/s
and
70km/h=19.44m/s

(30.56m/s-19.44m/s)/3.8m/s=t

t=11.12m/s/3.8m/s

t=2.9s

Answer 4

Thanks! One question: Do I have to convert km/h to m/s at the beginning? Will I get the same answer if I convert at the end?

Answer 5

Doesn't matter when you convert it, but the units have to be the same once you perform the calculations. Conversely, you could have just converted the acceleration from m/s to km/h. I thought it was easier to do by converting the velocity.

Best.