1. Multiple choice questions.
a. Which of the following is a contact force?
(i) Electrostatic force (ii)Frictional force (iii) Magnetic force (iv)Gravitational Force
Answer. (ii) Frictional force (Requires physical contact).
b. The SI unit of pressure is.
(i)N/m2 (ii) Nm2 (iii)N/m (iv) Nm
Answer. b. (i) N/m² (Pascal is the SI unit).
C. Which statement about the pressure exerted by a gas is correct?
i.Gases exert pressure in every direction
ii. Gases exert pressure only in upward direction
iii. Gases exert pressure in downward direction
iv. Gases exert pressure only at the bottom of a container.
Answer. c. (i)Gases exert pressure in every direction (Particles move randomly).
d. The atmospheric pressure is maximum-
i. at high altitude ii.at sea level
iii. at top of the mountain IV. in the desert
Answer. d. (ii) at sea level (Due to maximum air column weight).
2. Assertion and Reasoning
In the following questions, two statements are given – one labelled as Assertion A and the other labelled as Reason (R).
Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both A and R are true, and R is the correct explanation of the assertion.
(b) Both A and R are true, but R is not the correct explanation of the assertion.
(c) A is true, but R is false.
(d) A is false, but R is true.
(i) Assertion (A): Muscular force is a contact force.
Reason (R): To apply muscular force, there should be a physical contact between the objects.
(ii) Assertion (A): The bodies of submarines are made up of stronger and thicker material Reason (R). Submarines must endure the tremendous pressure exerted by water deep seas.
Answer.(i) (a) Both A and R are true, and R explains A (Muscular force needs contact, like lifting a box).
(ii) (a) Both A and R are true, and R explains A (Submarines withstand high water pressure at depth).
3. Answer the following questions in one word or one sentence.
a. Define electrostatic force.
Answer. Force between charged objects (e.g., a balloon sticking to a wall).
b. What is one atmospheric pressure?
Answer. b. One atmospheric pressure: 101,325 Pa (or 1 atm) at sea level.
c. State the relationship between pressure, force and area.
Answer. Pressure = Force/Area (P = F/A).
d. Give one example of atmospheric pressure.
Answer. Example: Drinking through a straw (air pressure pushes liquid up).
4. Answer the following questions in 2-3 sentences.
a. What is net force? If two forces of 10 N and 20 N act is same direction, then what is the net force?
Answer.Net force is the total force acting on an object. If 10 N and 20 N act in the same direction, net force = 10 + 20 = 30 N.
b. What are the effects of force?
Answer. Force can:
- Change an object’s speed/direction (e.g., kicking a ball).
- Alter shape/size (e.g., stretching a spring).
c. A porter puts a piece of cloth on his head to carry heavy loads. Give reasons.
Answer. The cloth increases the area (A) of contact, reducing pressure (P = F/A) on the head, making it easier to carry heavy loads.
d. Describe gravitational force.
Answer. It’s an attractive force between masses. Earth’s gravity pulls objects downward (e.g., apples falling from trees).
e. Calculate the pressure produced by a force of 450 N acting on an area of 5 m2.
Answer. Given: Force = 450 N, Area = 5 m².
Pressure (P) = F/A = 450/5 = 90 N/m² (or 90 Pa).