Class 9 Physics Unit-4: Turning Effect of Forces, Solved MCQs With Verified Answers. (Sindh Textbook Board, Jamshoro)

1. A pair of unlike parallel forces having different lines of force produce----------

(a) equilibrium
(b) torque
(c) a couple
(d) unstable equilibrium

... Answer is (c) a couple
Two unlike parallel forces of the same magnitude but not acting along the same line form a couple

2. Head to tail rule can be used to add forces.

(a) two
(b) three
(c) four
(d) any number of

... Answer is (d) any number of
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3. A force of 15 N makes an angle of 60° with horizontal. Its vertical component will be:

(a) 15 N
(b) 10 N
(c) 13 N
(d) 7 N

... Answer is (c) 13 N
Fy = F sin θ = 12.990 N

4. A body is in equilibrium when it has

(a) uniform speed
(b) uniform acceleration
(c) both a and b
(d) zero acceleration

... Answer is (d) zero acceleration
When a body does not possess any acceleration neither linear nor angular it is said to be in equilibrium. Zero acceleration is the fundamental characteristic for a body to be in equilibrium.

5. A body is in stable equilibrium after a slight tilt of its Centre of gravity

(a) remains above the point of contact
(b) remains on one side of the point of contact
(c) passes over the point of contact
(d) is at the lowest position

... Answer is (a) remains above the point of contact
A body is in stable equilibrium if when slightly displaced and then released it returns to its previous position.

6. A body is in unstable equilibrium after a slight tilt of its centre of gravity

(a) remains on one side of the point of contact
(b) remains above the point of contact
(c) passes over the point of contact
(d) is positioned at its bottom

... Answer is (b) remains above the point of contact
A body is in stable equilibrium if when slightly displaced and then released it does not return to its previous position.

7. A body is in neutral equilibrium when it's Centre of gravity :

(a) is at the lowest position
(b) remains at the same height
(c) is at the highest position
(d) is at its base

... Answer is (c) remains at the same height
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8. Bunsen burner is made stable by

(a) Increasing its length
(b) Increasing its mass
(c) Decreasing its base area
(d) Increasing its base area

... Answer is (d) Increasing its base area
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9. A tightrope walker carries a long pole to

(a) Increase his weight
(b) Raise his Centre of gravity
(c) Lower his Centre of gravity
(d) Keep his Centre of gravity in a fixed position

... Answer is (c) Lower his Centre of gravity
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10. Stability of a racing car is increased by

(a) Increasing its height
(b) Raising its Centre of gravity
(c) Decreasing its width
(d) Lowering its Centre of gravity

... Answer is (d) Lowering its Centre of gravity
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