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POST UTME UNILAG 2021 Physics | Objective

Are you preparing for POST UTME UNILAG exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2021 Physics (Objective) questions designed to simulate the real exam environment.

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Question 1

A radioactive sample of Δₗ emits Δₗπ particles with a half-life of 3.8 days. If 25% of the sample remains after 11.4 days, what is the decay cons\tant λ?

Correct A. \( λ = 0.0183 , \text{day}^{-1} \)

B. \( λ = 0.0187 , \text{day}^{-1} \)

C. \( λ = 0.0191 , \text{day}^{-1} \)

D. \( λ = 0.0195 , \text{day}^{-1} \)

Correct Answer: A

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Question 2

A convex lens of focal length 20 cm is placed in contact with a concave lens of focal length -30 cm. What is the focal length of the combination?

Correct A. \( f = 10 , \text{cm} \)

B. \( f = -10 , \text{cm} \)

C. \( f = 15 , \text{cm} \)

D. \( f = -15 , \text{cm} \)

Correct Answer: A

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Question 3

A 5 kg block is susp\ended from a spring with a spring cons\tant of 200 N/m. If the block is displaced by 0.2 m from its equilibrium position and released, what is the maximum speed of the block?

Correct A. \( v_{\text{max}} = 2.0 , \text{m/s} \)

B. \( v_{\text{max}} = 2.2 , \text{m/s} \)

C. \( v_{\text{max}} = 2.4 , \text{m/s} \)

D. \( v_{\text{max}} = 2.6 , \text{m/s} \)

Correct Answer: A

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Question 4

A particle of mass 2 kg is moving in a circular path of radius 3 m with a cons\tant speed of 4 m/s. What is the magnitude of the force acting on the particle?

Correct A. \( F = 8 , \text{N} \)

B. \( F = 10 , \text{N} \)

C. \( F = 12 , \text{N} \)

D. \( F = 15 , \text{N} \)

Correct Answer: A

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Question 5

A 100 W light bulb is connected to a 220 V power source. What is the current drawn by the bulb?

Correct A. \( I = 0.45 , \text{A} \)

B. \( I = 0.50 , \text{A} \)

C. \( I = 0.55 , \text{A} \)

D. \( I = 0.60 , \text{A} \)

Correct Answer: A

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Question 6

A 2 kg block is attached to a horizontal, massless spring with a force cons\tant of 100 N/m. The block is displaced by 0.2 m from its equilibrium position and released from rest. Assuming the block undergoes simple harmonic motion, calculate the maximum speed of the block as it passes through its equilibrium position.

A. 1.0 m/s

B. 2.0 m/s

Correct C. 3.0 m/s

D. 4.0 m/s

Correct Answer: C

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Question 7

A circuit consists of a 12 V battery, a 4 Ω resistor, and an unknown resistor R. The current in the circuit is 2 A. U\sing Kirchhoff's laws, calculate the value of R.

A. 2 Ω

Correct B. 4 Ω

C. 6 Ω

D. 8 Ω

Correct Answer: B

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Question 8

A particle of mass 0.5 kg is moving in a circular path of radius 2 m with a cons\tant speed of 4 m/s. Calculate the magnitude of the force acting on the particle.

A. 10 N

Correct B. 20 N

C. 30 N

D. 40 N

Correct Answer: B

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Question 9

A heat engine operates between two reservoirs at temperatures 500 K and 300 K. The engine produces 100 J of work per cycle. Calculate the efficiency of the engine.

A. 20%

B. 30%

Correct C. 40%

D. 50%

Correct Answer: C

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Question 10

A projectile is launched from the ground with an initial velocity of 20 m/s at an angle of 60° above the horizontal. Calculate the maximum height reached by the projectile.

A. 10 m

B. 15 m

Correct C. 20 m

D. 25 m

Correct Answer: C

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Question 11

A particle of mass 2 kg is moving in a circular path of radius 3 m with a cons\tant speed of 4 m/s. If the particle is subjected to a centripetal force of 12 N, what is the magnitude of the acceleration of the particle?

A. 12 m/s^2

Correct B. 16 m/s^2

C. 20 m/s^2

D. 24 m/s^2

Correct Answer: B

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Question 12

A 10 μF capacitor is connected in series with a 20 Ω resistor and a 50 V battery. What is the current flowing through the circuit?

A. 0.25 A

Correct B. 0.5 A

C. 0.75 A

D. 1 A

Correct Answer: B

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Question 13

A wave has a frequency of 50 Hz and a wavelength of 2 m. What is the speed of the wave?

A. 10 m/s

B. 20 m/s

Correct C. 30 m/s

D. 40 m/s

Correct Answer: C

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Question 14

A radioactive sample has a half-life of 10 days. If the initial activity is 1000 Bq, what is the activity after 20 days?

A. 500 Bq

Correct B. 750 Bq

C. 1000 Bq

D. 1250 Bq

Correct Answer: B

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Question 15

A particle is in a state described by the wave function ψ(x) = Ae^\( -αx^2 \). What is the expectation value of the position operator?

A. 0

Correct B. 1/α

C. 1/2α

D. 1/4α

Correct Answer: B

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Question 16

A light ray passes through a prism and is re\fracted. If the angle of incidence is 30° and the angle of re\fraction is 20°, what is the angle of deviation?

A. 40°

B. 50°

Correct C. 60°

D. 70°

Correct Answer: C

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Question 17

A block of mass 5 kg is attached to a horizontal spring with a spring cons\tant of 100 N/m. If the block is displaced by 2 m from its equilibrium position and released, what is the maximum speed of the block?

A. 2 m/s

B. 4 m/s

Correct C. 6 m/s

D. 8 m/s

Correct Answer: C

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Question 18

A sound wave has a frequency of 200 Hz and a wavelength of 0.5 m. What is the speed of the sound wave?

A. 100 m/s

Correct B. 200 m/s

C. 300 m/s

D. 400 m/s

Correct Answer: B

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Question 19

A circuit consists of a 10 Ω resistor, a 20 Ω resistor, and a 5 Ω resistor connected in parallel. What is the equivalent resis\tance of the circuit?

A. 5 Ω

B. 10 Ω

Correct C. 15 Ω

D. 20 Ω

Correct Answer: C

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Question 20

A quantum particle has a wave function given by ψ(x) = Ae^\( -αx^2 \). What is the probability density of the particle?

Correct A. A^2e^\( -2αx^2 \)

B. A^2e^\( -αx^2 \)

C. A^2e^\( αx^2 \)

D. A^2e^\( -2αx^4 \)

Correct Answer: A

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Question 21

A thermodynamic system undergoes a process from state A to state B, where the internal energy change is given by \( Delta U = Q - W \). If the system absorbs 500 J of heat and does 200 J of work, what is the change in internal energy?

Correct A. 600 J

B. 400 J

C. 200 J

D. -200 J

Correct Answer: A

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Question 22

A magnetic field is produced by a current-carrying wire. If the current is 2 A and the wire is 0.5 m long, what is the magnetic field strength at a point 0.2 m away from the wire?

A. 0.02 T

Correct B. 0.04 T

C. 0.06 T

D. 0.08 T

Correct Answer: B

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Question 23

A body is moving in a circular path with a cons\tant speed of 4 m/s. If the radius of the circle is 2 m, what is the centripetal acceleration?

A. 2 m/s^2

B. 4 m/s^2

Correct C. 6 m/s^2

D. 8 m/s^2

Correct Answer: C

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Question 24

A 100 Ω resistor is connected in series with a 200 Ω resistor and a 300 Ω resistor. What is the total resis\tance?

A. 200 Ω

B. 300 Ω

C. 400 Ω

Correct D. 600 Ω

Correct Answer: D

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Question 25

A 12 V battery is connected to a circuit with a 4 Ω resistor. What is the current flowing through the circuit?

A. 1 A

B. 2 A

C. 3 A

Correct D. 4 A

Correct Answer: D

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