SOLUTION: Suppose you’re driving 90.0 kilometers an hour and suddenly see red flashing lights in the rearview mirror. “Great,” you think, and you pull over, taking 20.0 seconds to come
Question 1160717: Suppose you’re driving 90.0 kilometers an hour and suddenly see red flashing lights in the rearview mirror. “Great,” you think, and you pull over, taking 20.0 seconds to come to a stop. What was your average acceleration, in m/sec2? Found 2 solutions by ikleyn, jim_thompson5910:Answer by ikleyn(52778) (Show Source): You can put this solution on YOUR website! .
The speed is V = 90 km/h = 90000 m/h = m/s = 25 m/s.
The acceleration is a = = = m/s^2 = 1.25 m/s^2 ANSWER
----------------
It is deceleration, in this case, instead of acceleration.
Solved, answered, calculated, explained and completed.
To convert from 90 km/hr to km/sec, we divide by 3600
This is the same as multiplying by (1/3600)
90 km/hr = (90 km/hr)*(1 hr/3600 sec)
90 km/hr = (90)*(1/3600) km/sec
90 km/hr = 0.025 km/sec
To convert from km/sec to m/sec, we multiply by 1000 since there are 1000 meters in 1 km
0.025 km/sec = (0.025 km/sec)*(1000 m/1 km)
0.025 km/sec = (0.025*1000) m/sec
0.025 km/sec = 25 m/sec
To wrap things up so far,
90 km/hr = 25 m/sec
Vi = initial velocity = 25 m/sec
Vf = final velocity = 0 m/sec
t = change in time = 20 seconds
a = acceleration
a = (Vf-Vi)/t
a = (0-25)/20
a = -25/20
a = -1.25
Negative acceleration indicates the object is slowing down. A counter force of the brakes is being applied opposite of the car's initial direction.
Average acceleration is -1.25 m/sec^2
Every second, the car slows down by 1.25 m/sec.