Answer:
5a. -0.4 m/s²
5b. 290 m
6. 12.9 s
7. 100 s
8. 17.2 km/hr
Step-by-step explanation:
5. "While approaching a police officer parked in the median, you accelerate uniformly from 31 m/s to 27 m/s in a time of 10 s.
a. What is your acceleration?
b. How far do you travel in that time?"
Given:
v₀ = 31 m/s
v = 27 m/s
t = 10 s
Find: a and Δx
v = at + v₀
(27 m/s) = a (10 s) + (31 m/s)
a = -0.4 m/s²
Δx = ½ (v + v₀) t
Δx = ½ (27 m/s + 31 m/s) (10 s)
Δx = 290 m
6. "If a pronghorn antelope accelerates from rest in a straight line with a constant acceleration of 1.7 m/s², how long does it take for the antelope to reach a speed of 22 m/s?"
Given:
v₀ = 0 m/s
v = 22 m/s
a = 1.7 m/s²
Find: t
v = at + v₀
(22 m/s) = (1.7 m/s²) t + (0 m/s)
t = 12.9 s
7. "A 1200 kg airplane starts from rest and moves forward with a constant acceleration of 5 m/s² along a runway that is 250 m long. How long does it take the plane to travel the 250 m?"
Given:
v₀ = 0 m/s
a = 5 m/s²
Δx = 250 m
Find: t
Δx = v₀ t + ½ at²
(250 m) = (0 m/s) t + ½ (5 m/s²) t²
t = 100 s
8. "During a marathon, a runner runs the first 10 km in 0.58 hours, the next 10 km in 0.54 hours and the last 10 km in 0.62 hours. What is the average speed of the runner during that marathon?"
This isn't a constant acceleration problem, so there's no need for a chart.
Average speed = total distance / total time
v = (10 km + 10 km + 10 km) / (0.58 hr + 0.54 hr + 0.62 hr)
v = 30 km / 1.74 hr
v = 17.2 km/hr
, we need to isolate x in terms of y:
and 
and 
and 
