# General Science - Physics MCQs

Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examinations.

31. Which of the following is NOT correct about Vectors addition?

[A] Vectors addition is associative

[B] Vectors addition is commutative

[C] Vectors of different natures can be added

[D] None of the above

Show Answer

**Correct Answer:** C [Vectors of different natures can be added]

**Notes:**

Vectors addition is associative and commutative. But vectors of the same nature alone can be added. Example: a Force vector cannot be added to velocity vector as they are of different nature.

32. When one body is actually moving over the surface of other body, the friction is known as:

[A] Kinetic friction

[B] Limiting friction

[C] Static friction

[D] Negative friction

Show Answer

**Correct Answer:** A [Kinetic friction]

**Notes:**

When one body is actually moving over the surface of other body, the friction is known as Kinetic friction. It is also known as dynamic friction.

33. The Newton’s third law is applicable when:

[A] bodies are at rest

[B] bodies are in motion

[C] bodies are in the air

[D] bodies are at rest or in motion

Show Answer

**Correct Answer:** D [bodies are at rest or in motion]

**Notes:**

The Newton’s third law is applicable whether the bodies are at rest or in motion. It states that to every action there is an equal and opposite reaction.

34. Which of the following is correct about the coefficient of limiting friction between any two surfaces in contact?

[A] it is equal to twice the tangent of angle of friction

[B] it is equal to twice the sine of angle of friction

[C] it is equal to the tangent of angle of friction

[D] it is equal to the sine of angle of friction

Show Answer

**Correct Answer:** C [it is equal to the tangent of angle of friction]

**Notes:**

The coefficient of limiting friction between any two surfaces in contact is equal to the tangent of angle of friction between them. u = tan Q where u = coefficient of limiting friction and Q = angle of friction

35. Which of the following is NOT correct about units of work:

[A] 1 joule = 10^{7} ergs

[B] 1 kg-m = 1 joule

[C] 1 kg-m = 9.8 joule

[D] 1 joule = 1 Nm

Show Answer

**Correct Answer:** B [1 kg-m = 1 joule]

**Notes:**Joule is the absolute unit of work in S.I 1 joule = 1 Nm

- 1 joule= 10
^{7} ergs (erg is the unit of work in c.g.s) - 1 erg = 1 dyne cm
- Also, Kilogram-metre (kg-m) is the gravitational unit of work on S.I 1 kg-m = 9.8 j

36. Which of the following is true about universal gravitational constant in the case of two bodies each of unit mass having their centres placed at unit distance apart?

[A] It is equal to the force of attraction between them

[B] It is equal to twice the force of attraction between them

[C] It is equal to half the force of attraction between them

[D] It is equal to ten times the force of attraction between them

Show Answer

**Correct Answer:** A [It is equal to the force of attraction between them]

**Notes:**

The universal gravitational constant is equal to the force of attraction between two bodies each of unit mass having their centres placed at unit distance apart. F = Gm_{1}m_{2}/r When m_{1} and m_{2} = 1 and r=1 then F=G.

37. Which of the following is correct about acceleration due to gravity?

[A] it increases with depth

[B] it decreases with depth

[C] it is independent of depth

[D] None of the above

Show Answer

**Correct Answer:** B [it decreases with depth]

**Notes:**

The value of acceleration due to gravity decreases with depth. g_{0}= g(1-d/R) where d is the depth below the centre of the earth.

38. At sea level, what is the difference between the value of acceleration due to gravity at the poles and at the equator?

[A] No difference

[B] 9.8 cm s^{-2}

[C] 1.80 cm s^{-2}

[D] None of the above

Show Answer

**Correct Answer:** C [1.80 cm s^{-2}]

**Notes:**

At sea level, the difference between the value of acceleration due to gravity at the poles and at the equator is 1.80 cm s^{-2}. The value of acceleration due to gravity increases as we go from equator to the poles.

39. Which of the following is correct about the value of acceleration due to gravity?

[A] it is greater at mountains than in plains

[B] it is lesser at mountains than in plains

[C] it is equal for mountains and plains

[D] None of the above

Show Answer

**Correct Answer:** B [it is lesser at mountains than in plains]

**Notes:**

The value of acceleration due to gravity decreases with increase in height. Therefore, it is lesser at mountains than in plains.

40. What is the value of Universal Gravitational Constant?

[A] 6.67×10^{-9} N–m2 kg–2

[B] 6.67×10^{-10} N–m2 kg–2

[C] 6.67×10^{11} N–m2 kg–2

[D] 6.67×10^{-11} N–m2 kg–2

Show Answer

**Correct Answer:** D [6.67×10^{-11} N–m2 kg–2]

**Notes:**

The value of Universal Gravitational Constant is same throughout the universe and is equal to 6.67×10^{-11} Nm^{2} kg^{-2} in S.I. and 6.67×10^{-8} dyne cm^{2} g^{-2}

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