Q1: If the area of an object is less than the pressure acting on that object will be
(c) Independent of area
(d) None of the above
Q2: Even though stone also attracts earth towards itself, earth does not move
(a) Because of greater mass of earth
(b) Because of lesser mass of stone
(c) Force exerted by stone is less
(d) Force exerted earth is large
Q3: Which of the statements is correct?
(a) Mass is constant and weight is variable
(b) Mass is variable and weight is constant.
(c) Both Mass and weight are variable
(d) Both Mass and weight are constant.
Q4: Weight of the object is:
(a) More at the equator and less at poles
(b) More at poles and less at equator
(c) Same at poles and equator
(d) Depend on Mass of the object
Q5: An object is put one by one in three liquids having different densities. The object floats with 1/9, 2/11 and 3/7 parts of their volumes outside the liquid surface in liquids of densities d1, d2 and d3respectively. Which of the following statement is correct?
(a) d1 > d2 > d3
(b) d1 > d2 < d3
(c) d1 < d2 > d3
(d) d1 < d2 < d3
Q6: In the relation F = GM mld2, the quantity G
(a) depends on the value ofg at the place of observation
(b) is used only when the Earth is one of the two masses
(c) is greatest at the surface of the Earth
(d) is universal constant of nature
Q7: Law of gravitation gives the gravitational force between
(a) the Earth and a point mass only
(b) the Earth and Sun only
(c) any two bodies having some mass
(d) two charged bodies only
Q8: The value of quantity G in the law of gravitation
(a) depends on mass of Earth only
(b) depends on radius of Earth only
(c) depends on both mass and radius of Earth
(d) is independent of mass and radius of the Earth
Q9: Two particles are placed at some distance. If the mass of each of the two particles is doubled, keeping the distance between them unchanged, the value of gravitational force between them will be
(a) 1/4 times
(b) 4 times
(c) 1/2 times
Q10: The atmosphere is held to the Earth by
(d) Earth’s magnetic field
(i) The value of g on the earth is about Six times of that on the moon.
(ii) In fluids (liquids and gases), pressure acts in All directions, and pressure increases as the depth increases.
(iii) If the area of a snow shoe is five times Bigger than the area of an ordinary shoe, then the pressure of a snow shoe on the snow is five times smaller.
(iv) Force acting on a unit area is called Pressure.
(v) The weight of an object on the earth is about Six times of its weight on the moon.
3. Quantity of matter contained in a body
4. The property due to which a body immersed in fluid experiences upward force.
5. Acceleration due to gravity of moon is how much time that of Earth
7. Whenever objects fall towards the Earth under gravitational force alone, we say that objects are in
8. The force with which a body is attracted towards the Earth
10. Force of gravitation due to Earth is called
11. Nature of gravitational force is always
1. Force between two bodies due to their masses
2. Thrust on unit area
6. Mass per unit volume
9. SI unit of pressure
5. One sixth
7. Free fall
1. Gravitational force
Q1: A man of mass 60 Kg is standing on the floor holding a stone weighing 40 N. What is the force with which the floor is pushing him up?
Ans: The gravitational pull on the man = Mg
= 60 x 10 = 600 N
The weight he is carrying = 40 N
The total downward force on the floor = 40 N + 600 N
= 640 N
The Gravitational force and upward force of the floor is an action – reaction pair.
The force with which the floor pushes the man = 640 N.
Q2: State Archimedes Principle?
Ans: According to Archimedes Principle when a body is partially or completely immersed in a fluid, experiences an up thrust which is equal to the weight of fluid displaced.
Q3: Why does a block of plastic released under water come up to the surface of water?
Ans: Since of plastic has density very less as compared to water i.e. weight of plastic is less than the buoyant force experienced by it therefore a block of plastic released under water come up to the surface of water/floats.
Q4: Why will a sheet of paper fall slower than one that is crumpled into a ball?
Ans: A greater surface area offers greater resistance and buoyancy same is true in the case of a sheet of paper that has larger surface area as compared to paper crumpled into a ball. So sheet of paper falls slower.
Q5: Why is it difficult to hold a schoolbag having a strap made of a thin and strong string?
Ans: It is difficult to hold a schoolbag having a strap made of a thin and strong string because a bag of that kind will make its weight fall over a small area of the shoulder and produce a greater pressure that makes holding the bag difficult and painful.
Q6: What makes a body to float or sink in a liquid?
Q7: What is the importance of universal law of gravitation?
The universal law of gravitation is important due to the following:
Q8: What happens to the force between two objects, if
(i) The mass of one object is doubled?
(ii) The distance between the objects is doubled and tripled?
(iii) The masses of both objects are doubled?
(i) The force between two objects will be doubled.
(ii) The force between two objects will become 1/4th and 1/9th of the present force.
(iii) The force between two objects will become four times the present force.
Q9: State the universal law of gravitation.
According to Newton’s universal law of gravitation:
Ans: Every mass in this universe attracts every other mass with a force which is directly proportional to the product of two masses and inversely proportional to the square of the distance between them.
Q10: What do you mean by buoyancy?
Ans: It is the upward force experienced by an object when it is immersed into a fluid.
|1. What is the formula for gravitational force?|
|2. What is the value of the gravitational constant?|
|3. What is the difference between mass and weight?|
|4. How does the gravitational force change with distance?|
|5. What is the significance of the gravitational force in the universe?|