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A newton force is defined as that force which when acting on a body of mass of 1 kg produces an acceleration of 1m/s² in it.

a) Equal and opposite 

b) Vector and kg.m/s 

c) Accelerated, rate, and momentum 

d) Magnitude and directions 

e) Momentum and force

Less mass of the small car makes it easier to accelerate a small car than a large car because acceleration is inversely proportional to mass of the car

Newton is the SI unit of force.

It is easier to accelerate a small car than a large car because acceleration of the car is inversely proportional to the mass of the car.

Imagine that you are watching a volleyball match and suddenly the ball comes towards you. Due to your reflexes you hit the ball so that you do not get hurt. The ball moves away from you due to the action of your hand on it. But definitely your hands pain due to the impact of the ball. That is, whenever two bodies interact with each other, each exerts a force on the other. The force exerted by one of the two bodies is called the action force while the force exerted by the other is called the reaction force.

In the above example the force exerted by you on the ball is the action force and the force exerted by the ball on your hand is the reaction force.

Action and reaction forces act simultaneously but on different bodies. Let us find out why a rubber ball rebounds when it is thrown on a hard floor. It is due to the action and reaction forces that are acting simultaneously.

The ball exerts a force (action force) on the floor and the floor exerts an equal and opposite force (reaction force) on it. The rubber ball being light rebounds.

Based on such examples of action and reaction forces, Sir Isaac Newton gave the third law of motion “To every action, there is an equal and opposite reaction".

Law of conservation of momentum states that total momentum of the system remains conserved in the absence of external force.

Proof: Consider two bodies of mass m₁ and m₂ moving with initial velocity u₁ and u₂ respectively. The two bodies collide with each other for a time interval ‘t’. The velocity after collision be v₁ & v₂ respectively. Let F₁₂ be the force applied by m₁ on m₂ and F₂₁ be the force applied by m₂ on m_1.

Momentum of mass m₁ before collision = m₁ u₁

Momentum of mass m₂ before collision = m₂ u₂

Momentum of mass m₁ after collision = m₁ v₁

Momentum of mass m₂ after collision = m₂ v₂

Impulse = force × time = change in momentum

For mass m₁ :

F₁₂ t = m₁ v₁ - m₁ u₁ …………….(1)

For mass m₂:

F₂₁t = m₂ v₂ – m₂ u₂ ……………..(2)

Adding equation (1) & (2)

F₁₂ t+ F₂₁t = (m₁ v₁ - m₁ u₁) + (m₂ v₂ – m₂ u₂)

(F₁₂ + F₂₁ ) t = (m₁ v₁ + m₂ v₂) - (m₁ u₁ + m₂ u₂)

According to Newton’s third law:

F₁₂ = - F₂₁

F₁₂ + F₂₁ = 0

(m₁ v₁ + m₂ v₂) = (m₁ u₁ + m₂ u₂)

Final momentum = Initial momentum

Hence momentum is conserved.

A rockets works on the principle of action and reaction. In a rocket, the hot gases produced by the rapid burning of fuel rush out of a jet at the bottom of the rocket at a very high speed. The equal and opposite reaction force of the downward going gases pushes the rocket upward with a great speed.

The correct answer is b) always act on different bodies in opposite directions

Action and reaction act on two different bodies. But both are of equal magnitude but the act in opposite directions such that they are acting and reacting simultaneously.

Action and reaction act on two different bodies. Action and reaction are equal in magnitude but they act in opposite directions and there is simultaneous action and reaction.

Filing the prongs of a tuning fork reduces its mass and thereby raises its frequency. Applying a little wax to the prongs increases its mass and thereby reduces its frequency. Therefore, filing the prongs of the tuning fork of the lower frequency decreases the beat frequency while applying a little wax to its prongs increases the beat frequency.

Correct option is: (D) 357m/s

Correct option is: (D) 5

 B. \(\frac 3{2l}\)\(\sqrt{\frac Tm}\)

Correct option is (B) 50 cm

Correct option is (A) a node

True.

The relative speed between the magnet and the closed loop is one of the factors on which the magnitude of induced emf produced depends.

The induced potential difference depends upon the number of turns and the rate of change of magnetic flux with time. The induced current depends upon the resistance of the coil.

A=N; B=N; C=S; D=S; E=N; F=S

1. The pencil is sad when it is shortened and is not allowed to grow. 

2. The pencil feels happy when it is useful to the whole family.

The poet describes the speech of the pencil as dark because the lead from which pencil is made is black. The phrase ‘make my mark’ has additional metaphoric meaning in addition to its literal meaning. Its deeper meaning is to do something that makes one famous or successful; to do something that is very important or meaningful. In the case of the pencil, as it serves others tirelessly, ‘make a mark’ can be interpreted as doing useful work.

Tommy is the young child of the family. We see that he uses the pencil to draw untidy pictures like submarines, aeroplanes and cabbages. Hence he wouldn’t be a grown up.

Correct Answer is: B) blunt

Graphite is used as a lubricant in the form of graphite powder or mixed with petroleum jelly or with any lubricant oil to form graphite grease.

Graphite

Yes, current will flow through the circuit since graphite is a good conductor of electricity.

Correct answer is No

C₆₀ is called buckminsterfullerene.

In buckminsterfullerene, there are 32 rings, of them 12 are pentagonal rings and 20 are hexagonal rings.

Hydrogen gas make the flair e to put off with a pop sound. So we can test it by introducing a incense stick into the mouth of the container having gas.

1. Rain water with slight acidic nature is called Acid rain. 

2. Air pollution is a major cause of acid rains. 

3. Fuels like coal and petroleum emissions have sulphur dioxide and nitrogen dioxide etc. which react with rain water droplets and form sulphuric acid and nitric acid. 

4. These acids come along with rain water to cause acid rain.

The substances formed in neutralization reaction are water and salt.

Materials required to conduct a neutralization reaction are dilute hydrochloric acid (any acid), Sodium hydroxide solution (any base), Phenolphthalein indicator, Conical flask, Dropper.

Hydrogen gas has less weight than air. So balloon fill with hydrogen gas flies high.

Reaction of an acid and a base is called neutralization reaction.

1. Neutralization is a chemical reaction where acid and base react with each other to form salt and water. 

2. The bases in the antacids neutralize gastric juice and give us relief from acidity. 

3. When an ant bites, it injects formic acid into the skin. It causes pain and itching. We can neutralize the acid by rubbing the paste of baking soda on the place of bite. Baking Soda is a base and it neutralizes the formic acid. 

4. When soil becomes too acidic, farmers neutralize it by adding basic substances like quick lime (sunnam), potassium hydroxide etc,. 

5. When soil becomes too basic they neutralize it with organic substances like compost which release acidic substances into the soil.

pH scale : Strength of acid or base solution is measured in pH scale. This scale was introduced by Sorensen. The range of pH scale is from 0 to 14.

Aim: 

Acid reacts with metals and produces hydrogen gas 

Materials required: 

Conical flask, hydrochloric acid, zinc pieces, incense stick, match box. Procedure: Take 5g of zinc metal pieces in a conical flask. Pour 20 ml of dilute hydro-chloric acid into it. Now, observe what happens. 

Observation: 

The zinc pieces reacted with the hydrochloric acid and releases a gas. Test for hydrogen gas 

Now, introduce a incense stick into mouth of the conical flask. The flame of burning stick will put off with a pop sound. This is a test for hydrogen gas. Hydrochloric acid reacts with zinc metal and forms zinc chloride, releases hydrogen gas. This reaction can be written as a word equation, Zinc + hydrochloric acid → zinc chloride + hydrogen 

Conclusion: 

Hence, we can conclude that acids react with metals and release hydrogen gas.

Aim: 

Base reacts with metal and produces hydrogen gas. Material required : Conical flask, sodium hydroxide solution, zinc pieces, incense stick. 

Procedure: 

1. Take 5gr of zinc metal pieces in a conical flask, 

2. Pour 20 ml of sodium hydroxide solution in it. 

3. Heat the conical flask.

Observation : 

The zinc pieces reacts with base and releases gas.

Test for hydrogen gas : 

1. Now, introduce a incense stick into the mouth of the conical flask. 

2. The flame of incense stick will put off with a pop sound. 

3. This is a test for hydrogen gas. 

Conclusion : 

Bases react with metals and produce hydrogen gas. 

Note : 

All bases do not react with metals.

Yes, but exert more pressure downwards than upwards.

Carbon dioxide gas put off the fire. So we can test it by introducing a lighting match stick into the mouth of the container having gas.

A dam is thicker at the bottom than at the top because the forces exerted are strongest close to the ground. Water pressure increases proportionally with depth, so the lower portion of the dam has greater water pressure exerted upon it. The increasing thickness of the lower dam also helps it support its own weight.

1. Take some crushed egg shells in a test tube and pour dilute sulphuric acid until the egg shells completely sink. Egg shell is made of calcium carbonate. 

2. We will observe that a gas being released. 

3. Bring a lighting match stick near the mouth of test tube. 

4. The gas that put off the lighting match stick indicating that the gas is carbon dioxide. 

5. This confirms that carbon dioxide releases when acid reacts with calcium carbonate.

Take some crushed egg shells in a test tube and pour dilute Hydrochloric acid until the egg shells completely sink. Egg shell is made of calcium carbonate. Bring a burning match stick near the mouth of test tube.

The gas that put off the burning match stick is carbon dioxide. It was released by the action of acid with calcium carbonate.

• Acids are used to make in batteries, fertilizers.
• Acids are used in preservation of food 

eg: vinegar.

Air pollution is a major cause of acid rains. So acid rains can be prevented by controlling the air pollution. To control air pollution

1. Reduce the usage of personal vehicles. 

2. Reduce the usage of fossil fuels. 

3. Encourage the usage of alternative sources of energy

4. Use electric vehicles. 

5. Use solar energy. 

6. Minimize use of fire and fire products. 

7. Treat and purify the industrial emissions before letting in to air. 

8. Plantation and reforestation should be done as much as possible.

pH scale is used to test for the strength of acids and bases.

All the liquids exert pressure on the base or bottom and walls of their container. All the liquid have weight. When we pour liquid into a vessel, then the weight of liquid pushes down on the base of the vessel producing a pressure.

The liquid exerts pressure on the base of the vessel.

The pressure exerted by a liquid changes with depth in the liquid. The pressure exerted by a liquid increases with increasing depth inside the liquid. The pressure exerted by a liquid is small just under the surface of the liquid. But as we go we deeper in a liquid the pressure of liquid increases. As the depth of liquid increases the weight of liquid column pushing down from above increases and hence the pressure also increases.

The force of attraction between all masses in the universe, especially the attraction of the earth’s mass for bodies near its surface. 

For example: When you hold a ball up in the air, the mass of Earth allows the ball to fall to the Earth.