Question
a stunt car driver testing the use of air bags drives a car at a constant speed of 25m/s for a total of 100 meters. he applies his brakes and accelerates uniformlu to a stop just as he reaches the wall 50 meters away. SKETCH THE A GRAPH SHOWING POSITION V.S TIME and VELOCITY v.s TIME
also how long does it take the car to travel the first 100 meters?
also how long does it take the car to travel the first 100 meters?
Answers
Damon
first do the stopping problem
d = Vi t + .5 a t^2
d = 25 t + .5 a t^2
50 = 25 t + .5 a t^2
v = Vi + a t
0 = 25 + at
a t = -25
a = -25/t
combine 50 = 25 t - .5(25t)
50 = .5 (25 t)
t = 4 seconds to stop after applying brakes
a = -25/4 while stopping
Now do the problem
for the first part
x = 25 t until t = 2 where x = 50
then x = 50 + 25(t-2) - (25/8) (t-2)^2
until stopped at x = 100 and t = 6
during deacceleration v = 25 -(25/4)(t-2)
d = Vi t + .5 a t^2
d = 25 t + .5 a t^2
50 = 25 t + .5 a t^2
v = Vi + a t
0 = 25 + at
a t = -25
a = -25/t
combine 50 = 25 t - .5(25t)
50 = .5 (25 t)
t = 4 seconds to stop after applying brakes
a = -25/4 while stopping
Now do the problem
for the first part
x = 25 t until t = 2 where x = 50
then x = 50 + 25(t-2) - (25/8) (t-2)^2
until stopped at x = 100 and t = 6
during deacceleration v = 25 -(25/4)(t-2)