Second Law of Motion

Q.

Why does a gun recoil when a bullet is fired?

Q.

The value of one newton

Q. State the three laws of motion.

Q.

An inclined plane making an angle ${30}^0$ with the horizontal is placed in a uniform horizontal electric field $200\raisebox{1ex}{$N$}\!\left/ \!\raisebox{-1ex}{$C$}\right.$ as shown in the figure. A body of mass of 1kg and the charge $5mC$ is allowed to slide down from rest from a height of $1m$. If the coefficient of friction is $0.2$, find the time taken by the body to reach the bottom.

1. $2.3s$

2. $0.46s$

3. $1.3s$

4. $0.92s$

Q.

An object of mass 100 kg is accelerated uniformly from a velocity of 5 m/s to 8 m/s in 6 s. Calculate the initial and final momentum of the object. Also, find the magnitude of the force exerted on the object.

Q.

An $8000kg$ engine pulls a train of $5$ wagons, each of $2000kg$, along a horizontal track. If the engine exerts a force of $40000N$ and the track offers a friction force of $5000N$, then calculate: (a) the net accelerating force (b) the acceleration of the train (c)the force of wagon $1$ on wagon $2$.

Q.

What is the relation between SI and CGS unit of force?

Q.

A stone dropped from the top of a building, takes 4 seconds to reach the ground. Find the height of the building.

Q.

State Newtons second law of motion and show that the first law of motion can be mathematically stated from the Newtons seconds law.

Q. Question 5
A stone is thrown in a vertically upward direction with a velocity of $5m{s}^{-1}$. If the acceleration of the stone during its motion is $10m{s}^{-2}$ in the downward direction, what will be the height attained by the stone and how much time will it take to reach there?

Q.

Why is force is said to be the rate of change of momentum and not the change in velocity?

Q. Question 3
A train starting from a railway station and moving with uniform acceleration attains a speed 40 kmph in 10 minutes. Find its acceleration.

Q.

A bullet of mass 20 gram is horizontally fired with a velocity 150 metre per second from a pistol of 2 kilogram what is the recoil velocity of the stock

Q. Of the following quantities, which one has dimensions different from the remaining three:

1. Force per unit area
2. Energy per unit volume
3. Angular momentum per unit mass
4. Product of voltage and charge per unit volume

Q. What is acceleration ? Write it's unit

Q.

What is the relation between the weight of an object on the moon and that on the earth?

Q. Find the force needed to speed up a car of mass 1000 kg with a rate of 5 $m{s}^{–2}$.

1. 200 N
2. 5000 N
3. 2000 N
4. 500 N

Q. Why is the gravitational power of the earth is zero at its centre?

Q.

The rate of change of velocity is called _________.

Q.

Is force a scalar quantity?

Q.

A constant retarding force of 50N is applied to a body of mass 20kg moving with the speed of 15m/s. How long does the body take to stop?

Ans1 Given

F=50N

M=20kg

u=15m/s

v=0

As F=ma

a=50/20=2.5m/s^2

Since the retarding is negativd so -2.5 m/s^2

Time=

v=u+at

=0-15/-2.5=6s

Ans2 F=ma

50=20×0-15/t

50=20×-15/t

50/20×-15=1/t

-6 s=t

Why the 2 is incorrect ?

Q.

Is angular momentum constant in uniform circular motion?

Q.

Define one newton of force.

Q.

A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of $400m$ in $20s$. Find its acceleration. Find the force acting on it if its mass is $7metrictons$ (Hint: $1metricton=1000kg$).

Q. Question 8
An automobile vehicle has a mass of 1500 kg. What must be the force between the vehicle and road if the vehicle is to be stopped with a negative acceleration of 1.7 $m{s}^{-2}$?

Q.

Which of the following has more inertia: (a) a rubber ball and a stone of the same size? (b) a bicycle and a train? (c) a five-rupee coin and a one-rupee coin?

Q.

A bus starts from rest and attains a speed of $36km/h$ in $1minute$ while moving with uniform acceleration along a straight road. Calculate the acceleration of the bus.

Q.

A machine gun of mass 10 kg fires 20 g bullets with a speed of 500 ms^-1 at the rate of 10 bullets per second. To hold the gun steady in its position, how much force is necessary.

1. 200 N

2. 500 N

3. 100 N

4. 250 N

Q.

A stone of $1kg$ is thrown with a velocity of $20m{s}^{-1}$ across the frozen surface of a lake and comes to rest after travelling a distance of $50m$. What is the force of friction between the stone and the ice?

Q.

Write the derived unit of force.