in general
v = Vi + a t
x = Xi + Vi t + (1/2) a t^2
Phase 1, stop 1 to stop 2
v= 0 + 2 t = 40
x = 0 + 0 + (1/2) 2 t^2
so
t = 20
x = 400 meters
Phase 2 stop 2 to stop 3
Vi = 40
Xi = 400
t = 30 so 50 seconds so far
v = 40 constant
x = 400 + 40*30 = 1600 at stop 3
Phase 3 , stop 3 to end
t = 10 so 60 seconds for trip
v = 0 = 40 + a (10) so a = -4 m/s^2
x = 1600 + 40*10 - (1/2)4*100 = 1800 at end
A bus on a straight road starts from rest at a bus stop and accelerates at 2 m/s2 until it
reaches a speed of 40 m/s. Then the bus travels for 30 s at a constant speed in the same
direction until the driver sees the next bus stop in the distance. The driver applies the
brakes, stopping the bus in a uniform manner in 10 s.
a. Plot a rough v vs t graph for the entire trip. (Hint: There are 3 segments with
different accelerations.)
b. What is the acceleration of the bus at t = 10 s? t = 40 s? t = 55 s?
c. How long does the bus take to travel from the first bus stop to the second bus stop?
d. What is the average velocity of the bus during the trip?
1 answer
3 answers