If a car is traveling at a speed of 60 mi /hr, what constant (negative) acceleration will enable it to stop in 9 sec ?

Expert Answers

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For this we can use equations for motion.

V = at + V0

V  = final velocity

a  = accelaration

t  = time

V0= Initial velocity

 

For our question;

V  = 0 mi/s

a  = ????

t  = 9 s

V0= 60 mi/hr = 60/(3600) mi/s = 1/60 m/s

 

V = at + V0

a = (V-V0)/t

  = (0-1/60)/9 m/s^2

  = 0.00185 mi/s^2

 

The constant negative accelaration (deccelaration) of the car is 0.00185 mi/s^2.

 

 

 

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The initial speed of the car is 60 mi/hr or `60/3600` mi/s. It has to come to a halt in 9 seconds.

The required negative acceleration for this to happen is `(0 - 1/60)/9 = 1/540` mi/s^2

The required acceleration to bring the car to a halt in 9 s is -1/540 mi/s^2.

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