Question

A car having mass of 1000 kg is moving at a speed of 30m/s brakes are applied to bring tthe car to rest if the friction between the tyre and road surface is 5000n.calculate tthe time in which the car will come to rest

Answer 1

Given :

• Mass (m) = 1000 kg
• Initial velocity (u) = 30 m/s
• Final velocity (v) = 0 m/s
• Force (F) = -5000 N

To Find :

• Time in which it will come to rest

Solution :

First we've to find out acceleration with which car is moving. Then we've to apply 1st equation of motion for calculating time. Here force is taken as negative because it is frictional force and applied in a direction of motion.

⇒F = ma

⇒a = F/m

⇒a = -5000/1000

⇒a = -5

$\therefore$ Acceleration with which car is moving is -5 m/s²

• Negative sign of acceleration shows that it is applied in opposite direction of motion. Negative acceleration is also known as Retardation.

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Now, use 1st equation of motion,

⇒v = u + at

⇒v - u = at

⇒t = (v - u)/a

⇒t = (0 - 30)/-5

⇒t = -30/-5

⇒t = 30/5

⇒t = 6

$\therefore$ Time in which it will come to rest is 6 seconds.