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increase in depth

It is about 10⁵ Pa.

(c) The assertion is true, but the reason is false

1. True

2. False - Pressure can be increased by increasing the force.

3. True

4. True

5. False - Pressure is inversely proportional to the area of contact.

6. False - The pressure in a liquid increase with depth.

Since, there are many actions which give us the feeling of force like we hit or catch many objects in our regular routine. Most of the times, we see that the moving ball stops after sometime and it changes the direction of motion when it is hit by a bat also, when we compress a spring, its shape and size changes.

The atmospheric pressure at sea level is nearly 100,000 Pa

The pressure exerted by the air in the atmosphere is called atmospheric pressure. The numerical value of atmospheric pressure at sea level is 1.01325 bar or 101325 Pascal.

True The atmospheric pressure is nearly 10⁵ Pa.

Atmospheric pressure refers to the number of air molecules per unit area. As we go to higher altitude, the number of air molecules decreases which results in a decrease in the magnitude of force exerted by them. So the atmospheric pressure will be greater at ground level.

No, we cannot lift or push a book lying on a table without touching it, because it is a type of contact forces.

Lowers pressure, High pressure.

(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion

Correct explanation:

The weight of the bags falls on larger area of shoulder. So lesser pressure is produced.

It will come to the surface of water. 

[Note: This is because its density is less than that of water. When it floats, the unbalanced force acting on it is zero.]

The air below the table top exerts pressure 101 × 10³ Pa on it in the upward direction. Hence, the table top doesn’t crumble down.

(d) All the above

Broader straps are provided on a back – pack for giving less pressure on the shoulders by providing a larger area of contact with the shoulder

The air pressure at the sea level is about 101 × 10 Pa. This is the pressure that we carry on our heads. The cavities in our body are filled with air, and arteries and veins are filled with blood. Their pressure balances the pressure due to the atmosphere. Hence, we don’t feel the atmospheric pressure.

The pressure produced by a given force depends on the area of the surface on which the force acts. The greater the surface area, the less is the pressure produced. Load carrying heavy vehicles have large number of wheels so that the load (weight, force) is distributed over large surface area of the wheels in contact with the road. Hence, the pressure decreases and the tyres do not burst.

Heavy vehicles have broad tyres because broad tyres have a large area of contact and thus exert less pressure on the ground. Because of this, heavy vehicles can move even on soft roads and fields without sinking.

If the magnitudes of the two forces are unequal then the net force acting on the object is the difference between the two forces and the object will moves towards the direction of the larger force applied.

The gravitational pull of the earth increases and the stone falls down.

The diagram showing all the forces acting on an object at a particular instant is called free body diagram.

i) Net force in the vertical direction = + 6N – 6N = 0N

ii) Net force in the horizontal direction = + 20N – 3N = 17N.

Magnetic field: The space around the magnet where its influence can be detected s called the magnetic field

The object is said to be at rest when no forces are acting on it or net force acting on it is zero. So the statement should be corrected like this “Because the car is at rest, no forces are acting on it or net force on the car is zero.”

Yes, we can agree with this statement. Net force can increase or decrease the speed of an object. Force can also change the direction of an object. Hence we conclude that net force can change the state of motion of an object. Some examples:

1. If we kick the ball it will move from state of rest. 

2. If we stop the running ball it will come to state of rest. 

3. If we through a ball on the ground it will come to rest after sometime due to gravitational force acting on it. 

4. If we pull the chair, it will move due to muscular force acting on it.

Free body diagram: The diagram showing all the forces acting on an object at a particular instant is called the free body diagram

B) Spring balance

The tools meant for cutting have sharp edges because of smaller contact area they exerts more pressure on objects and cutting of objects are easy.

Limiting friction is the force of static friction acting just before the body starts moving

Pressure: The force acting perpendicularly on a unit area of a surface is called pressure

1. The gravitational force acting on an object is called its weight. 

2. Greater force must be applied to lift a greater weight.

1. Force has magnitude as well as direction.
2. A change in the speed of the object or the direction of its motion or both implies a change in its state of motion.
3. The algebraic sum of all forces acting on a body is known as net force and is denoted before 
4.  A force can change the state of motion of an object. 
5. Force may cause a change in the shape of an object. 
6. The force acting on the unit area of a surface is called pressure

Muscular force: The force exerted by body muscles is coiled muscular force.

The machines that run on muscular force are : 

1. Bicycle 

2. Hand cart 

3. Boat 

4. Cycle rickshaw 

5. Stretching of a spring

6. Ball pen 

7. Vegetable chopper 

8. Sharpener 

9. Pulley 

10. Fruit peeler

The force which occurs without any physical contact between two objects is known as force at a distance or field force.

The force which we exert by using our body muscles is known as muscular force.

The resistance to the movement of a body over the surface of another body is called friction.

B) electrostatic force

(d) Pressure at A< Pressure at B<Pressure at C

Electrostatic force.

1. The weight of the rocket downwards. 

2. The upward force due to firing of rocket.

Tension: The tightness of rope or string when it is stretched is called tension.

Yes, in the wet mud the friction is very less and wet mud acts as a lubricant between our feet and floor. During rainy season the mud or road will be wet and as mentioned above the friction will be less, so most accidents happen

Yes, it was due to less friction between my foot and floor.

(b) electrostatic force.

A) Gravitational force

When we stretch a rope or a string the tightness of rope or string is called tension. Tension is a contact force.

The reason is everything on earth experienced by a large gravitational force of earth so remaining gravitational forces are negligible.