Wednesday

July 23, 2014

July 23, 2014

Posted by **Shreyas** on Monday, January 6, 2014 at 1:09am.

How fast is the blue car going 3.6 seconds after it starts? Answer: 12.96 m/s

How fast is the blue car going 8.8 seconds after it starts? Answer: 16.2 m/s

How far does the blue car travel before its brakes are applied to slow down? Answer: 154.71 m/s

These problems I had difficulty solving for. So any help is greatly appreciated. Thanks.

What is the acceleration of the blue car once the brakes are applied?

What is the total time the blue car is moving?

What is the acceleration of the yellow car?

- Physics -
**Damon**, Monday, January 6, 2014 at 2:59amat 3.6 seconds v = a t = 3.6*3.6 = 12.96 m/s

at 4.5 s

v = a t = 3.6*4.5 = 16.2 m/s

x(position) = d (distance traveled)

= average speed (16.2/2) * time (4.5)

= 8.1 m/s * 4.5 s = 36.45 meters

speed remains 16.2 until t = 4.5+7.3 = 11.8 seconds

at 4.5 + 7.3 = 11.8 seconds

v = 16.2 still

d = 16.2 * 7.3 = 118.26 m

so

x = 118.26 + 36.45 = 154.71 meters

at end

v = 0

so

average v = (16.2+0)/2 = 8.1 m/s

d = 201 - 154.71 = 46.29 meters to stop

time to stop = 46.29/8.1 = 5.71

acceleration while braking = (0-16.2)/5.71 = -2.84 m/s^2

so

total time = 5.71 + 11.8 = 17.5 s

so

yellow car goes 201 meters in 17.5 seconds

201 = a t^2 = a (17.5)^2

a yellow = .656 m/s^2

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