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# Category Archives: Force

## A simple numerical on momentum

**Car mass is 1200 kg moving velocity is 108 km/hr. On applying brakes velocity reduced to 36 km/hr. Find change in momentum?**

*(posted by Aditi)*

Answer:

m=1200 kg

u=108 x 5/18=30m/s

v=36×5/18=10m/s

Change in momentum = m(v-u) = 1200 x (30-10)=1200 x 20= __24000 kg m/s__

## Numerical Problem from Friction

“The friction coefficient between a road and the tyre of a vehicle is 4/3.find the maximum incline the road may have so that once hard brakes are applied and the wheel starts skidding,the vehicle going down at a speed of 10m/s is stopped within 5m” Raju Rabha asked

## Numerical Problem from Motion of Connected systems

Two blocks A and B of mass m1 and m2 respectively are kept in contact on a frictionless table.The experimenter pushes the block A from behind so that the blocks accelerate. If the block A exerts a force F on the block B,what is the force exerted by the experimenter on A.

## Solving problems from kinematics and friction

I just want to know how to easily solve problems related to kinematics and friction. I don’t know why i always face problem in these two topics a lot……

Please help and tell some tricks to solve these both…….

THANK U

## How to tackle problems with constraint relations?

“Can you suggest a way to tackle problems on constraint relations easily??” – Aritra posted this question.

**Answer**: The common way to solve problems involving constraints is to replace the constraints with their reaction forces. As the question is not specific, I cannot tell much now. If you have further doubts regarding this issue, please post as comments to this post.

## What is resultant force?

Shaz asks:

“What is resultant force?”

Answer:

When a number of frces are acting simultaneously on a body, it will be producing an **effect** – may be keeping the body in equilibrium, or giving it an acceleration in a particular direction.

**Resultant **of a number of forces is defined as that single force which can replace all other forces to produce the **same effect**.

If the number of forces acting on the body keep it at rest or maintain uniform motion,it is said to be in equilibrium; then the resultant is zero (since acceleration is zero).