41. The inner diameter of a small test tube can be measured accurately using a

**A.**Micrometres screw gauge**B.**Pair of dividers**C.**Metre rule**D.**Pair of vernier calliper

**Correct Option: Answer is D**

A vernier scale is a visual aid to take an accurate measurement reading between two graduation markings on a linear scale by using mechanical interpolation; thereby increasing resolution and reducing measurement

**42. **A pulley system has three pulleys in the fixed block and two in the movable block and if the pulley has an efficiency of 72%, the mechanical advantage of the system is?

**A.**36.0**B.**7.2**C.**5.0**D.**3.6

**Correct Option: Answer is D**

MA = E × Vr/100

So

MA = 72 × 5 = 360/100 = 3.6

**43. **When an atom loses or gain a charge it becomes

**A.**An electron**B.**An ion**C.**A neutron**D.**A proton

**Correct Option: Answer is B**

If an atom gains or loses an electron, it becomes an ion. An atom that gains a negative electron, it becomes a negative ion. If it loses an electron it becomes a positive ion

**44. **A ball of mass 800g moving horizontally with a speed of 5m/s hits a vertical wall and rebounds with the same speed. The impulse experienced by the ball is?

**A.**0kgm**B.**2kgm/s**C.**4kgm/s**D.**8kgm/s

**Correct Option: Answer is D**

Initial momentum = (0.8) × (5)

= 4.0kgms\(^{-1}\)

Final momentum

= (0.8) × (– 5)

= – 4.0kgms\(^{-1}\)

Impulse on ball

= Change in momentum

= 4.0 – (– 4.0)

= 8.0.0kgms\(^{-1}\)

**45. **The force between the molecules of a liquid in contact with that of a solid is?

**A.**Adhesive**B.**Cohesive**C.**Magnetic**D.**Repulsive

**Correct Option: Answer is B**

**Cohesion, in physics**, the inter-molecular attractive force acting between two adjacent portions of a substance, particularly of a solid or liquid

**46. **A body of mass 100g moving with a velocity if 10ms-1 collides with a wall. If after collision it moves with a velocity of 2.0ms−1 in the opposite direction, calculate the change in momentum.

**A.**0.8Ns**B.**1.2Ns**C.**12.0Ns**D.**80.0Ns

**Correct Option: Answer is A**

Momentum = Mass x Velocity

Change in Momentum = Mass x (change in velocity)

Change in Momentum = Mass x (v – u)

Mass = 100g = 0.1kg

U = 2ms−1

V = 10ms−1

Change in momentum = m (v − u)

= 0.1 (10 − 2)

= 0.1 (8)

= 0.8Ns

**47. **A 20kg mass is to be pulled up a slope inclined at 30° to the horizontal. If efficiency of the plane is 75%. The force required to pull the load up the plane is J [g=10ms−2]

**A.**87N**B.**73.5N**C.**133.3N**D.**533.2N

**Correct Option: Answer is C**

V. R = \(\frac{1}{Sinθ}\)

m = 20kg

V.R = \(\frac{1}{Sin 30}\)

= 2

Efficiency = 75%

Load = mg

= 20 x 10 = 200N

Efficiency = \(\frac{M.A}{V.R} \times 100\)

75/100 = \(\frac{M.A}{2}\)

M .A = \(\frac{75 \times 2}{100}\)

M. A = 1.5

Since M. A. = \(\frac{\text{Load}}{\text{Force}}\)

Force = \(\frac{200}{1.5}\)

= 133.3N

**48. **The tendency of a body to remain at rest when a force is applied to it is called.

**A.**Impulse**B.**Momentum**C.**Inertia**D.**Friction

**Correct Option: Answer is C**

**Inertia** is the resistance of any physical object to any change in its velocity. This includes changes to the object’s speed, or direction of motion. An aspect of this property is the tendency of objects to keep moving in a straight line at a constant speed, when no forces act upon them.

**49. **An object is placed 20cm from a concave mirror of focal length 10cm. The linear magnification of the image produced is?

**A.**0**B.**$\frac{\mathrm{1/}}{2}$**C.**1**D.**2

**Correct Option: Answer is C**

\(\frac{I}{V}\) = \(\frac{1}{f}\) – \(\frac{1}{u}\)

\(\frac{I}{V}\) = \(\frac{1}{10}\) – \(\frac{1}{20}\)

= \(\frac{1}{20}\) V

V = 20cm.

M = \(\frac{V}{U}\)

= \(\frac{20}{20}\)

= 1

**50. **The energy needed to move a unit positive charge around a complete electric circuit is called the

**A.**electromotive force**B.**electric potential difference**C.**electric energy**D.**kinetic energy

**Correct Option: Answer is B**

Electric potential difference: work needed per unit of charge to move a test charge between the two points.

Electric energy: energy derived from electric potential energy.

Kinetic energy: moving energy