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# Tag Archives: numerical

## Numerical from Motion and Force for CBSE Class 9 SA1

*A steam engine of mass 30000 kg pulls 2 wagons each of mass 20000 kg with an acceleration of 0.2 m/s/s. neglecting frictional force calculate (i) the force exerted by the engine (ii) the force experienced by each wagon*

(Srija posted)

**Answer**:

In this case the engine is pulling the rest of the wagons.

The force exerted by the engine = total mass of the wagons x acceleration = 2 x 20000 x 0.2 = **8000 N**

Each wagon experiences a net force = 20000 x 0.2 = **4000 N**

## Motion of a charge particle in an electric field – Numerical Problem

At t=0 a very small object with mass 0.400mg and charge +9.00μC is travelling at 125 m/s in the -x-direction. The charge is moving in a uniform electric field that is in the +y-direction and that has magnitude E= 895 N/C. The gravitational force on the particle can be neglected. How far is the particle from the origin at t= 7.99 ms.

* Hint for solving the above problem*:

displacement along X direction; x=-u_{x}t=125 x 7.99/1000

Displacement along Y direction, y=0.5 a_{y} t^{2}

a_{y}=qE/m

s=√(x^{2}+y^{2})

Just substitute the values and get the answer

## 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.

## A Numerical from Combination of thin lenses in contact

Two thin lenses of focal lengths f1=20cm and f2=60cm are placed in contact. find the focal length f3 of the combined lenses. find also the focal length f of a third lens placed in contact with these two that would result in overall focal length f11=-40cm. (Asked Young)

## A Numerical Problem on conservation of momentum – An exploding shell

An 80 kg shell is flying at a speed of 36km/h. It explodes into two pieces and one piece of mass 20 kg stops. What is the velocity of other piece?

(It’s a simple problem. Expect the visitors to answer soon)