Major Competitive Exams
Q. If A = {x | x is an even integer} and B = {x | x is a prime number}, what is A ∩ B?
A.
{2}
B.
{2, 3}
C.
{2, 4}
D.
{}
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Solution
The only even prime number is 2, so A ∩ B = {2}.
Correct Answer: A — {2}
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Q. If A = {x | x is an even number} and B = {x | x is a multiple of 3}, what is A ∪ B?
A.
{0, 2, 4, 6, ...}
B.
{0, 3, 6, 9, ...}
C.
{0, 2, 3, 4, 6, 9, ...}
D.
{0, 1, 2, 3, ...}
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Solution
The union A ∪ B includes all even numbers and all multiples of 3. Thus, A ∪ B = {0, 2, 3, 4, 6, 9, ...}.
Correct Answer: C — {0, 2, 3, 4, 6, 9, ...}
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Q. If A = {x | x is an even number} and B = {x | x is a prime number}, what is A ∩ B?
A.
{2}
B.
{2, 3}
C.
{2, 4}
D.
{}
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Solution
A ∩ B = {2} as 2 is the only even prime number.
Correct Answer: A — {2}
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Q. If A = | 1 2 | | 3 4 |, find det(A).
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Solution
det(A) = (1)(4) - (2)(3) = 4 - 6 = -2.
Correct Answer: B — 2
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Q. If A = | 1 2 | | 3 4 |, what is det(A)?
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Solution
det(A) = (1*4) - (2*3) = 4 - 6 = -2.
Correct Answer: B — 2
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Q. If A = | 1 2 | | 3 5 |, what is det(2A)?
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Solution
det(2A) = 2^2 * det(A) = 4 * (1*5 - 2*3) = 4 * (-1) = -4.
Correct Answer: C — 20
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Q. If a bag contains 4 green and 6 yellow marbles, what is the probability of picking a yellow marble?
A.
2/5
B.
3/5
C.
4/5
D.
1/5
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Solution
Total marbles = 4 + 6 = 10. Probability of yellow = 6/10 = 3/5.
Correct Answer: B — 3/5
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Q. If a bag contains 4 green and 6 yellow marbles, what is the probability of picking a green marble?
A.
2/5
B.
4/10
C.
4/6
D.
1/3
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Solution
Total marbles = 4 + 6 = 10. Probability of green marble = 4/10 = 2/5.
Correct Answer: A — 2/5
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Q. If a battery provides a voltage of 9 V and is connected to a circuit with a total resistance of 3 ohms, what is the power consumed by the circuit?
A.
27 W
B.
18 W
C.
9 W
D.
3 W
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Solution
Power P = V^2 / R. Here, P = 9^2 / 3 = 81 / 3 = 27 W.
Correct Answer: B — 18 W
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Q. If a beam is supported at both ends and a load is applied at the center, what is the reaction force at each support?
A.
Equal to the load
B.
Half the load
C.
Double the load
D.
Zero
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Solution
In this case, the reaction force at each support is half the load applied at the center.
Correct Answer: B — Half the load
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Q. If a beam of light passes through a prism with an angle of 60 degrees and the refractive index of the prism is √3, what is the angle of minimum deviation?
A.
30 degrees
B.
60 degrees
C.
45 degrees
D.
15 degrees
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Solution
Using the formula for minimum deviation, D = (n - 1)A. Here, n = √3 and A = 60 degrees. Thus, D = (√3 - 1) * 60 degrees, which approximates to 30 degrees.
Correct Answer: A — 30 degrees
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Q. If a bill is introduced in the Lok Sabha and it takes 3 readings to pass, and each reading takes 5 days, how many days does it take to pass the bill?
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Solution
Total days = 3 readings * 5 days per reading = 15 days.
Correct Answer: B — 15
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Q. If a bill is introduced in the Lok Sabha and it takes an average of 15 days to pass, how many days will it take to pass 5 such bills?
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Solution
Total days = 5 bills * 15 days/bill = 75 days.
Correct Answer: A — 60
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Q. If a block is on a horizontal surface and a force is applied at an angle, how does this affect the normal force acting on the block?
A.
Increases normal force
B.
Decreases normal force
C.
No effect on normal force
D.
Depends on the angle
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Solution
Applying a force at an angle reduces the normal force because part of the applied force acts vertically upward, counteracting the weight of the block.
Correct Answer: B — Decreases normal force
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Q. If a boat can travel 20 km upstream in 4 hours, what is the speed of the current if the speed of the boat in still water is 10 km/h?
A.
2 km/h
B.
3 km/h
C.
4 km/h
D.
5 km/h
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Solution
Speed upstream = distance/time = 20/4 = 5 km/h. Speed of current = speed of boat - speed upstream = 10 - 5 = 5 km/h.
Correct Answer: A — 2 km/h
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Q. If a boat can travel at 15 km/h in still water and the current is 5 km/h, what is the speed of the boat upstream?
A.
10 km/h
B.
15 km/h
C.
20 km/h
D.
25 km/h
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Solution
Speed upstream = speed of boat - speed of current = 15 - 5 = 10 km/h.
Correct Answer: A — 10 km/h
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Q. If a body has a moment of inertia of 15 kg m² and is subjected to a torque of 5 N m, what is its angular acceleration?
A.
0.33 rad/s²
B.
0.5 rad/s²
C.
1 rad/s²
D.
3 rad/s²
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Solution
Angular acceleration α = τ/I = 5 N m / 15 kg m² = 0.33 rad/s².
Correct Answer: A — 0.33 rad/s²
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Q. If a body is moving in a circular path with a constant speed, what type of acceleration does it experience?
A.
Centripetal acceleration
B.
Linear acceleration
C.
Angular acceleration
D.
No acceleration
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Solution
A body moving in a circular path experiences centripetal acceleration directed towards the center of the circle.
Correct Answer: A — Centripetal acceleration
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Q. If a body is moving in a circular path with a constant speed, which of the following statements is true?
A.
The body is in equilibrium
B.
The net force acting on the body is zero
C.
The body experiences a centripetal force
D.
The body has no acceleration
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Solution
A body moving in a circular path with constant speed experiences a centripetal force directed towards the center of the circle.
Correct Answer: C — The body experiences a centripetal force
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Q. If a body is moving in a circular path with a radius of 10 m and completes one full revolution in 5 seconds, what is its angular velocity?
A.
0.2 rad/s
B.
1.25 rad/s
C.
2 rad/s
D.
4 rad/s
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Solution
Angular velocity (ω) = 2π/T = 2π/5 = 1.25 rad/s.
Correct Answer: B — 1.25 rad/s
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Q. If a body is moving in a circular path with uniform speed, which of the following statements is true?
A.
The body has no acceleration
B.
The body has constant velocity
C.
The body experiences centripetal acceleration
D.
The body moves in a straight line
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Solution
The body experiences centripetal acceleration directed towards the center of the circle.
Correct Answer: C — The body experiences centripetal acceleration
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Q. If a body is moving in a straight line and no external torque acts on it, what can be said about its angular momentum?
A.
It is zero
B.
It is constant
C.
It increases
D.
It decreases
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Solution
Angular momentum remains constant if no external torque acts.
Correct Answer: B — It is constant
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Q. If a body is rotating with an angular momentum L and its moment of inertia is halved, what will be the new angular momentum if the angular velocity remains constant?
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Solution
Angular momentum L = Iω; if I is halved and ω remains constant, L remains L.
Correct Answer: A — L
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Q. If a body moves in a circular path with a constant speed, which of the following statements is true?
A.
The body has zero acceleration
B.
The body has constant acceleration
C.
The body has uniform velocity
D.
The body experiences centripetal acceleration
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Solution
The body experiences centripetal acceleration directed towards the center of the circle.
Correct Answer: D — The body experiences centripetal acceleration
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Q. If a box contains 3 red balls and 2 blue balls, what is the probability of randomly selecting a red ball?
A.
1/2
B.
3/5
C.
2/5
D.
1/5
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Solution
Total balls = 3 + 2 = 5. Probability of selecting a red ball = Number of red balls / Total balls = 3/5.
Correct Answer: B — 3/5
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Q. If a capacitor has a capacitance of 10 µF and is charged to 5 V, what is the charge on the capacitor?
A.
50 µC
B.
5 µC
C.
2 µC
D.
10 µC
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Solution
The charge (Q) on a capacitor is given by Q = C * V. Here, Q = 10 µF * 5 V = 50 µC.
Correct Answer: A — 50 µC
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Q. If a capacitor is charged and then short-circuited, what happens to the charge on the capacitor?
A.
It remains the same
B.
It is discharged
C.
It increases
D.
It becomes zero
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Solution
When a charged capacitor is short-circuited, the charge flows through the circuit, and the charge on the capacitor becomes zero.
Correct Answer: B — It is discharged
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Q. If a capacitor is charged to 12V and has a capacitance of 6μF, what is the stored energy? (2022)
A.
0.432 mJ
B.
0.072 mJ
C.
0.864 mJ
D.
0.216 mJ
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Solution
Energy = 0.5 × C × V² = 0.5 × 6 × 10^-6 × 12² = 0.432 mJ.
Correct Answer: A — 0.432 mJ
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Q. If a capacitor is charged to a voltage of 5 V and then disconnected from the battery, what happens to the charge on the capacitor if the voltage is increased to 10 V? (2023)
A.
Charge increases
B.
Charge decreases
C.
Charge remains the same
D.
Charge becomes zero
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Solution
When the voltage is increased to 10 V, the charge on the capacitor increases because charge (Q) is directly proportional to voltage (V) for a given capacitance.
Correct Answer: A — Charge increases
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Q. If a capacitor is charged to a voltage V and then connected in parallel with an uncharged capacitor, what will be the final voltage across both capacitors?
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Solution
When connected in parallel, charge redistributes, and the final voltage across both capacitors will be V/2.
Correct Answer: B — V/2
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