"A car starts from rest and travels for 7.0 s with a uniform acceleration of +3.0 m/s2" -----> distance = 1.5t^2
a = 3 m/s^2
v = 3t + c
when t = 0 , v = 0 (it started from rest) , so c = 0
v = 3t
s = 1.5^2 + k
when t = 0, s = 0, then k = 0
so s = 1.5t^2
so how far has it gone in 7 s ?
s = 1.5(49) or 73.5 m, with a velocity of 3(7) or 21 m/s
2nd stage:
a2 = -2.5
v2 = -2.5t + c
here c = 21
and s2 = -1.25t^2 + 21t + 0
after 2 seconds of this
s2 = -1.25(4) + 21(2) or 37 m
so the car went 73.5 m in the first stage and another 37 slowing down,
so it went 110.5 m
check my arithmetic
A car starts from rest and travels for 7.0 s with a uniform acceleration of +3.0 m/s2. The driver then applies the brakes, causing a uniform acceleration of −2.5 m/s2. If the brakes are applied for 2.0 s, determine each of the following.
How far has the car gone?
1 answer
1 answer