Gravitation Test

Result

Gravitation Test - 15

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Question 1
1 / -0

An object immersed in a liquid experiences a buoyant force. The direction of the buoyant force acting on the object will

A
always be upward

B
always be downward

C
be upward if the density of the object is less than that of the liquid and vice versa

D
be downward if the density of the object is less than that of the liquid and vice versa

Solution

Buoyant force is a characteristic force exerted by all liquids on objects immersed (either partially or fully) in them. This force, irrespective of the densities of the object and liquid, always acts in the upward direction.

The correct answer is A.
Question 2
1 / -0

Use the following information to answer the next question.

The weight of an object changes in water as it displaces 20 kg of the water. The mass of this object is 60 kg.

What is the weight of the object in water?

A
392 N

B
568 N

C
528 N

D
784 N

Solution

Mass of the object, m = 60 kg

Acceleration due to gravity, g = 9.8 m/s²

Weight of the object in air, W_a = 60 × 9.8 = 588 N

Mass of the displaced water, m_d = 20 kg

Weight of the displaced water, W_d = 20 × 9.8 = 196 N

According to Archimedes’ principle, if a body is immersed in water, then it looses its weight, which is equal to the weight of the water displaced by the body.

That is,

W_a− W_w = W_d; (W_W= Weight of the object in water)

∴W_w = W_a− W_d

= 588 − 196 = 392 N

The correct answer is A.

Question 3

1 / -0

Use the following information to answer the next question.

The densities of four objects are shown in the given table. Equal quantities of these objects are immersed in a jar filled with mercury (ρ = 13.59 g cm⁻³).
Object	Density (g/cm³)
I	0.34
II	7.87
III	0.86
IV	2.56

It will be observed that

all the four objects sink in mercury

all the four objects float in mercury

objects I and III float, while objects II and IV sink in mercury

objects II and IV float, while objects I and III sink in mercury

Solution

An object floats in a liquid if its density (or average density) is less than that of the liquid.

In the given situation, all the four objects have densities less than that of mercury. Hence, all four will float in mercury.

The correct answer is B.

Question 4
1 / -0

Use the following information to answer the next question.

The constant of proportionality in Newton’s law of gravitation is known as the universal gravitational constant (G). Its magnitude is a × 10^b Nm² kg⁻².

Which alternative represents the values of a and b?

A

a b

6.67 11

B

a b

9.87 −11

C

a b

6.67 −11

D

a b

9.87 11

Solution

The value of the universal gravitational constant (G) is 6.67 × 10⁻¹¹ Nm² kg⁻². Hence, the values of a and b are 6.67 and −11 respectively.

The correct answer is C.