Question

If on applying the brakes, a car of mass 800 kg traveling at 90 km/h experiences a retarding force of 450 N, what will be its velocity after travelling through a distance of 200 m?

Answer 1

Answer: velocity after travelling through 200 m = 20m/s

Explanation:

F= ma

450N=800kg x a m/s2

a= 9/16 m/s2

now using equation of motion : $v^{2} -u^{2} =2*a*s$

given v = 90km/hr = 90 x(5/18) m/s = 25 m/s

$25^{2} - u^{2} = 2* \frac{9}{16} *200\\u = 20 m/s$

Answer 2

Answer: Velocity of car after travelling through a distance of 200 m is 20m/s

Concept: Force = mass*acceleration

$v^{2} = u^{2} + 2as$

where v = final velocity

u = initial velocity

a = acceleration

s = distance travelled by the body

Given: Mass of car = 800kg

Speed of car = 90km/h

Retarding force = 450N

Distance = 200m

To find: Velocity of car after travelling through a distance of 200 m

Explanation:

Mass of car = 800kg

Speed of car = 90km/h = 25m/s

Retarding force = 450N

Distance = 200m

We have,

Force = mass*acceleration

450 = 800*a

a = 0.5625 m^2/s

The force is retarding force

Therefore, acceleration is opposite to the direction of velocity of car.

a = -0.5625 m^2/s

u = 25m/s

s = 200m

we have

$v^{2} = u^{2} + 2as$

v^2 = (25)^2 +2*(-0.5625)(200)

v^2 = 625 - 225

v^2 = 400

v = 20m/s

Answer: Velocity of car after travelling through a distance of 200 m is 20m/s

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