A parachute on a dragster racing-car opens and changes the speed of a car from 85 meters/second to 45 meters/second. Of this car is decelerating (slowing down) at a rate of -8.9 meters/ second, how many seconds will this take?
85 m/s - 45 m/s = 40 m/s = 9 m/s/s or 9 m/s^(2)
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4.5 seconds 4.5 sec
To find out how many seconds it will take for the car to change its speed from 85 m/s to 45 m/s while decelerating at a rate of -8.9 m/s, we can use the equation of motion:
v = u + at
where:
v = final velocity (45 m/s)
u = initial velocity (85 m/s)
a = acceleration (-8.9 m/s^2)
t = time (unknown)
Rearranging the equation to solve for time (t):
t = (v - u) / a
Substituting the given values:
t = (45 - 85) / -8.9
Calculating:
t = (-40) / -8.9
t ≈ 4.49 seconds
Therefore, it will take approximately 4.49 seconds for the car to change speed from 85 m/s to 45 m/s while decelerating at -8.9 m/s.