2. A car is moving with a speed of 27 m/s down a long, straight road. When it is

Question

2. A car is moving with a speed of 27 m/s down a long, straight road. When it is 130 m from a traffic light, the light turns red. (a) With what constant acceleration must the car move in order to stop at the light? (b) How long does it take the car to stop?

3. A building is 45 m long. You run along the front of the building on your way to try to catch a bus. When you pass the first end of the building, you are running at 2.2 m/s . You are running at 4.1 m/s when you pass the other end of the building. Assume that you ran with a constant acceleration as you passed in front of the building. (a) What was the value of your acceleration? (b) How long did it take you to pass the front of the building? (c) What was your average velocity during this time?

Please show work

Explanation / Answer

v^2 - u^2 = 2as

0 - 27^2 = 2*a*130

a = -2.8 m/s^2

t = v-u/a = 9.64 s

3) a) a = v^2-u^2/2s = ((4.1*4.1)-(2.2*2.2))/(2*45) = 0.133 m/s^2

b) Vavg = v + u/2 = (2.2+4.1)/2 = 3.15 m/s

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