1. You leave your home at noon hoping to get to your destination, which is 300 m

Question

1. You leave your home at noon hoping to get to your destination, which is 300 miles away, by 5 p.m. During the first two hours of your trip you encounter road construction and only average 40 mph. What average speed do you need to maintain for the rest of your journey to get there on time?

2. A cheetah can obtain a speed of 72 km/h from a standing start in just 2 s. What is its average acceleration?

3. A truck is travelling along a straight stretch of freeway at 25 m/s. How far will it travel in 10 s? If it accelerates at 25 m/s. How far will it travel in 10 s? If it accelerates at 2 m/s^2 to pass another truck, how far will it travel in the next 10 s?

4. A ball travelling at 16 m/s falls past a window. How far will it fall during the next 2 s?

5. assume that you are travelling 60 mph when you see a hazard ahead. If it takes you 1 s to recognize the hazard and apply the brakes, how far (in feet) will you travel during this second? If it takes you an additional 4 s to stop, how much farther will you travel?

Please show work.

Explanation / Answer

Number 1)

In the first 2 hours, you have gone 80 miles

That means that you have 300 - 80 = 220 miles left to go and 3 hrs to do it.

220/3 = 73.3 mph

Number 2)

72 km/hr converts to 20 m/s

Apply vf = vo + at

20 = 0 + a(2)

a = 10 m/s2

Number 3)

Part A)

d = vt

d = 25(10) = 250 m

Part B)

d = vot + .5at2

d = (25)(10) + (.5)(2)(10)2

d = 350 m

Number 4)

Apply d = vot + .5at2

d = (16)(2) + (.5)(9.8)(2)2

d = 51.6 m

Number 5)

Part A)

60 miles per hour = 88 feet per sec

That means you will travel 88 feet in that second

Part B)

d = (.5)(vf + vo)t

d = (.5)(0 + 88)(4)

d = 176 feet

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