Home
Class 11
PHYSICS
A driver of a car driving at 72 kmph not...

A driver of a car driving at `72 kmph` notices a child on the road at a distance of `50m`. If the weight of the car including the driver is `750kg` wt then calculate the resistive force applied on the wheels by the brakes, if the car, comes to stop just in front of the child.

Text Solution

Verified by Experts

Given `v_(0)=72kmph=72xx(5)/(18)`
`v_(0)=20ms^(-1)` `s=50m` `m=750kg`
We know that `v^(2)=v_(0)^(2)+2as` where `v=0`
`:.0=(20)^(2)+2a(50)` `:.a=-(400)/(100)=-4ms^(-2)`
We also know that `F=ma`
resistive force to the motion `=750xx4=3000N=3xx10^(3)N`.
Promotional Banner

Topper's Solved these Questions

  • LAWS OF MOTION

    SUBHASH PUBLICATION|Exercise Five mark question|4 Videos

  • KINETIC THEORY

    SUBHASH PUBLICATION|Exercise NUMERICALS WITH SOLUTIONS|19 Videos

  • MECHANICAL PROPERTIES OF FLUIDS

    SUBHASH PUBLICATION|Exercise NUMERICALS WITH SOLUTIONS|33 Videos

Similar Questions

Explore conceptually related problems

A driver of a car sights a child on the road at a distance of 200 m. If the speed of the car is 108 kmph then calculate the retardation and time taken to stop the car just in front of the child.

A driver of car moving at 20 ms^(-1) finds a child on the road 50 m ahead and stops the car 10 m earlier to the child. If the mass of the car with the driver is 1000 kg. Calculate the force exerted by the breaks on the car and the time taken to stop the car.

A car and a truck are going on a straight road each having a velocity of 72 km/h. The car cannot come to a stop in less than 3.0 sec and the truck takes 5.0 seconds time to stop on the high-way. The car is behind the truck. The truck gives a signal for stopping at a tollplaza. What should be the least distance of the car from the truck so that it does not bump onto the truck? (Take human response time to be 0.5 sec)

The makers of a certain motor car state that if the brakes are applied fully on a dry level road at 48 kmph, the vechicle will stop in 13m. A motorist while driving one of these cars on a level road was involved in an accident. However, if he claimed that he was proceeding at 32 kmph, and he had stopped in 3m after applying the brakes, then justify whether the claim was right or wrong.

A car is moving at 72kmph . Brakes are suddenly applied causing all the tyres to skid. How far will the car move before coming to a stop (given g=9.8ms^(-2) and mu=0.2 )?