Please answer all questions 7. A train normally travels at a uniform speed of 55
ID: 1652722 • Letter: P
Question
Please answer all questions 7. A train normally travels at a uniform speed of 55 km/h on a long stretch of straight, level track. On a perticular day, the traun must make a 1.70 stop at a station along this track. If the train decelerates at a uniform rate of 2.0 m/s and accelerates at a rate of 0.4 mai, how much time is lost itn stopping at the station? 8. A ball is thrown vertically upward from the edge of a bridge 22.0 m high with an initial speed of 11.0 m/'s. The ball falls all the way down and the water below. Determine the time it takes the ball to strike the water 9. A ball is thrown vertically downward from the edge of a bridge 22.0 m high with an initial speed of 11.0m's. The ball falls all the way down and strikes the water below. Determine the time it takes the ball to strike the water 10. An object initially at rest experiences an acceleration of 1.2 m/s i for 53 s then travels at that constant veloeity for another 10.0 s. What is the magnitude of the object's average velocity over the 15.3 s interval?Explanation / Answer
7. a. speed of train, u = 55 km/h = 15.2778 m/s
deceleration a= 2 m/s/s
acceleration A = 0.4 m/s/s
stop interval, T = 1.7 min
time lost at station = t1 + t2 + T
now, 0 = u - at1
t1 = u/a
and u = 0 + At2
t2 = u/A
so, time lost = 1.7 min + 15.2778/2 + 15.2778/0.4 = 2.l463 min
8. height of bridge, h = 22 m
u = 11 m/s iupwards
time = t
h = ut - 0.5gt^2
-22 = 11t - 4.9t^2
4.9t^2 - 11t - 22 = 0
t = 3.516 s
9. from previous problem
-22 = -11t - 4.9t^2
4.9t^2 + 11t - 22 = 0
t = 1.274 s
10. u = 0 m/s
a = 1.2 m/s/s
t1 = 5.3 s
t2 = 10s at constant velocity v
distance covered = 0.5at1^2 + (at1)t2 = 80.454 m
average velocity = 80.454/15.3 = 5.2584 m/s
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