# Second Law of Motion

## Trending Questions

**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.

$2.3s$

$0.46s$

$1.3s$

$0.92s$

**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 5 ms−1. If the acceleration of the stone during its motion is 10 ms−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:

- Force per unit area
- Energy per unit volume
- Angular momentum per unit mass
- 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 ms–2.

- 200 N
- 5000 N
- 2000 N
- 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 ms−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.

200 N

500 N

100 N

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.