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POST UTME GREENFIELD UNIVERSITY 2017 Physics | Objective

Are you preparing for POST UTME GREENFIELD UNIVERSITY exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2017 Physics (Objective) questions designed to simulate the real exam environment.

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Question 1

A particle of mass $m$ and charge $q$ is moving in a circular path of radius $R$ in a uniform magnetic field of strength $B$. If the particle's velocity is $v$, what is the magnitude of the magnetic force acting on it?

Correct A. \frac{mv^2}{R}

B. \frac{mv^2}{2R}

C. \frac{mv^2}{4R}

D. \frac{mv^2}{8R}

Correct Answer: A

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Question 2

A block of mass $M$ and density $\rho$ is floating in a fluid of density $\rho_f$. If the block is displaced by a dis\tance $x$ from its equilibrium position, what is the magnitude of the restoring force acting on it?

Correct A. \frac{\rho V g x}{\rho_f}

B. \frac{\rho V g x}{\rho}

C. \frac{\rho_f V g x}{\rho}

D. \frac{\rho V g x}{\rho V}

Correct Answer: A

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Question 3

A beam of light is pas\sing through a prism of angle $\theta$. If the re\fractive index of the prism is $n$, what is the angle of deviation of the light beam?

Correct A. \frac{2n\theta}{n-1}

B. \frac{n\theta}{n-1}

C. \frac{2\theta}{n-1}

D. \frac{\theta}{n-1}

Correct Answer: A

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Question 4

A gas of molecules is contained in a cylinder of volume $V$ and temperature $T$. If the gas is heated by an amount $\Delta T$, what is the change in its internal energy?

Correct A. \frac{3}{2}nR\Delta T

B. \frac{5}{2}nR\Delta T

C. \frac{7}{2}nR\Delta T

D. \frac{9}{2}nR\Delta T

Correct Answer: A

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Question 5

A thermodynamic system is undergoing a process in which its entropy is increa\sing. If the system is in contact with a heat reservoir at temperature $T$, what is the direction of heat flow?

A. Heat flows from the system to the reservoir

Correct B. Heat flows from the reservoir to the system

C. Heat flows in both directions

D. Heat flow is zero

Correct Answer: B

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Question 6

A parallel plate capacitor consists of two plates, each of area 0.04 m^2, separated by a dis\tance of 0.02 m. The capaci\tance of the capacitor is 8 nF. If a potential difference of 10 V is applied across the plates, calculate the energy stored in the capacitor.

A. 0.16 J

B. 0.32 J

Correct C. 0.64 J

D. 1.28 J

Correct Answer: C

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Question 7

A body of mass 2 kg is moving in a circular path with a cons\tant speed of 4 m/s. If the radius of the path is 3 m, calculate the centripetal force acting on the body.

A. 16 N

B. 32 N

Correct C. 64 N

D. 128 N

Correct Answer: C

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Question 8

A heat engine operates between two temperatures, 500 K and 300 K. If the efficiency of the engine is 30%, calculate the work done by the engine per cycle.

A. 100 J

B. 200 J

Correct C. 300 J

D. 400 J

Correct Answer: C

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Question 9

A light ray passes from air into a glass of re\fractive index 1.5. If the angle of incidence is 30°, calculate the angle of re\fraction.

A. 20°

B. 30°

Correct C. 40°

D. 50°

Correct Answer: C

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Question 10

A circuit consists of a 12 V battery, a 4 Ω resistor, and a 6 Ω resistor connected in series. If the current in the circuit is 2 A, calculate the voltage across the 6 Ω resistor.

A. 8 V

B. 12 V

Correct C. 16 V

D. 20 V

Correct Answer: C

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Question 11

A parallel plate capacitor has a capaci\tance of 10 μF and is charged to a potential difference of 20 V. If a dielectric slab of thickness 2 mm and dielectric cons\tant 4 is inserted between the plates, what is the new capaci\tance?

A. 40 μF

B. 50 μF

Correct C. 60 μF

D. 70 μF

Correct Answer: C

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Question 12

A radioactive sample has an initial activity of 100 Bq. After 2 hours, the activity decreases to 50 Bq. What is the half-life of the sample?

A. 1 hour

Correct B. 2 hours

C. 3 hours

D. 4 hours

Correct Answer: B

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Question 13

A 10 Ω resistor is connected in series with a 20 Ω resistor and a 30 Ω resistor. What is the total resis\tance?

A. 40 Ω

B. 50 Ω

Correct C. 60 Ω

D. 70 Ω

Correct Answer: C

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Question 14

A heat engine operates between a high-temperature reservoir at 500 K and a low-temperature reservoir at 300 K. What is the maximum efficiency?

A. 0.25

Correct B. 0.30

C. 0.35

D. 0.40

Correct Answer: B

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Question 15

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

A. 0.5 A

Correct B. 1 A

C. 2 A

D. 3 A

Correct Answer: B

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Question 16

A parallel plate capacitor has a capaci\tance of 2 μF. If a potential difference of 10 V is applied across it, what is the charge stored on each plate?

Correct A. 20 μC

B. 20 mC

C. 2 μC

D. 2 mC

Correct Answer: A

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Question 17

A radioactive sample decays from 100 g to 50 g in 10 years. What is the half-life of the sample?

A. 5 years

Correct B. 10 years

C. 15 years

D. 20 years

Correct Answer: B

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Question 18

A particle moves in a circular path with a radius of 2 m and a speed of 4 m/s. What is the magnitude of the acceleration of the particle?

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 19

A convex lens has a focal length of 20 cm. An object is placed 30 cm in front of the lens. What is the image dis\tance?

A. 10 cm

Correct B. 20 cm

C. 30 cm

D. 40 cm

Correct Answer: B

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Question 20

A vector has a magnitude of 5 units and makes an angle of 60° with the positive x-axis. What is the x-component of the vector?

Correct A. 2.5 units

B. 3.5 units

C. 4.5 units

D. 5.5 units

Correct Answer: A

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Question 21

A particle of mass $m$ is moving in a circular path of radius $r$ with a cons\tant speed $v$. The particle is subjected to a centripetal force $F_c$ given by $F_c = \frac{mv^2}{r}$. If the particle's speed is doubled to $2v$, what is the new centripetal force $F_c'$?

A. \frac{2mv^2}{r}

Correct B. \frac{4mv^2}{r}

C. \frac{mv^2}{2r}

D. \frac{mv^2}{4r}

Correct Answer: B

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Question 22

A parallel plate capacitor has a capaci\tance of $C = 2\,\mu\text{F}$ and is charged to a potential difference of $V = 10\,\text{V}$. If the dis\tance between the plates is doubled, what is the new capaci\tance $C'$?

A. 4\,\mu\text{F}

Correct B. 2\,\mu\text{F}

C. 1\,\mu\text{F}

D. 0.5\,\mu\text{F}

Correct Answer: B

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Question 23

A particle of mass $m$ is moving in a straight line with an initial velocity $v_0$ and is subjected to a cons\tant acceleration $a$. If the particle's velocity after time $t$ is given by $v = v_0 + at$, what is the particle's position after time $t$?

Correct A. \frac{1}{2}at^2 + v_0t

B. v_0t + at

C. \frac{1}{2}v_0t^2 + at

D. \frac{1}{2}at^2 - v_0t

Correct Answer: A

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Question 24

A wave of frequency $f$ and wavelength $\lambda$ is traveling through a medium with a speed $v$. If the wave's amplitude is doubled, what is the new intensity $I'$?

Correct A. 4I

B. 2I

C. I

D. \frac{1}{4}I

Correct Answer: A

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Question 25

A magnetic field of strength $B$ is directed perp\endicular to a current-carrying wire of length $L$. If the wire carries a current $I$, what is the magnitude of the magnetic force $F$ on the wire?

Correct A. ILB

B. \frac{ILB}{2}

C. \frac{ILB}{4}

D. \frac{ILB}{8}

Correct Answer: A

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