Technical Based Test Test 1 Nddc Scholarship
Question 31
When a body is moving along an inclined plane, the direction of frictional force is always
Correct answer: (c) opposite to the direction of motion
Friction always acts to oppose the relative motion (or impending motion) between surfaces in contact.
Not clear enough?
Question 32
The coefficient of friction is minimum for
Correct answer: (c) rolling friction
Rolling friction is much smaller than both static and dynamic (sliding) friction.
Not clear enough?
Question 33
A block of iron weighing 28 kg can be just pulled along a horizontal force of 12 kg.
Find the coefficient of friction.
Not clear enough?
Question 34
Heat produced in a resistor depends
Correct answer: (a) directly on time
From Joule’s law, H = I2Rt, heat produced is directly proportional to the time current flows.
Not clear enough?
Question 35
A 30volt battery is charged from 120volt d.c. supply, a resistor being connected in series with a battery to limit the charging current to 15 A. Find the rate at which energy is wasted as heat in the circuit.
Correct options: (c) 1.350 kJ
Given:\[V_s = 120 \ \text{V}, \quad V_b = 30 \ \text{V}, \quad I = 15 \ \text{A}\]
\[V_R = V_s - V_b = 120 - 30 = 90 \ \text{V}\]
\[P = I \times V_R = 15 \times 90 = 1350 \ \text{W}\]
Since 1 W = 1 J/s,\[P = 1350 \ \text{J/s} = 1.350 \ \text{kJ/s}\]
\[\boxed{\text{Rate of energy wasted} = 1.350 \ \text{kJ/s}}\]
Not clear enough?
Question 36
Liquid drops always occupy minimum surface area on account of
Correct answer: (b) surface tension
Surface tension pulls liquid molecules into the smallest possible surface area, giving drops their nearly spherical shape.
Not clear enough?
Question 37
Small drops of mercury are practically spherical because of
Correct answer: (a) predominant S.T. force
Surface tension dominates over gravity for small mercury drops, making them nearly spherical.
Not clear enough?
Question 38
Small liquid drops assume spherical shape because
Correct answer: (d) liquid tends to have the minimum surface area due to surface tension
Surface tension pulls the molecules inward, making the drop assume a shape with the smallest surface area — a sphere.
Not clear enough?
Question 39
A drop of water breaks into two droplets of equal size. In this process which of the following statements is correct.
Correct answer: (c) the sum of masses of the droplets is equal to the original mass of the drop
Mass is conserved when a drop splits, though surface area increases and radii change.
Not clear enough?
Question 40
When sugar is added to water, the surface tension of sugar solution is
Correct answer: (a) more than that of water
Dissolving sugar increases the cohesive forces in the solution, thereby increasing its surface tension compared to pure water.