A body is moving with uniform speed in a circular path. Which statement is correct? MCQ with Answer and Explanation

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A body is moving with uniform speed in a circular path. Which statement is correct?

A. Acceleration is zero

B. Acceleration is directed towards the center

C. Velocity is constant

D. No force acts on the body

Answer: Option B

Solution (By JKSSB Mock Tests)

In uniform circular motion, speed is constant but velocity direction changes continuously, requiring centripetal acceleration directed toward the center (a = v²/r). By Newton's second law, a centripetal force must act. Velocity isn't constant (direction changes); acceleration isn't zero; force is required. Memory tip: 'Uniform circular motion: constant speed, changing velocity, center-seeking acceleration'. This conceptual question tests understanding of circular dynamics, crucial for mechanics in competitive exams. Always distinguish speed (scalar) from velocity (vector) in motion analysis.

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Question #1

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In a photoelectric effect experiment, a graph is plotted between the stopping potential (V0) on the y-axis and the frequency of incident light (v) on the x-axis. The slope of this straight line gives the value of:

A. Planck's constant (h)

B. Work function of the metal

C. Planck's constant divided by electron charge (h/e)

D. Speed of light (c)

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Correct Answer: Option C

Explanation:
Einstein's photoelectric equation is K_max = hv - W. Since K_max = eV0 (where V0 is stopping potential), eV0 = hv - W. Rearranging for the y-axis variable gives V0 = (h/e)v - (W/e). This is a linear equation y = mx + c. The slope 'm' of the V0 vs v graph is strictly exactly h/e.

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Question #2

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Due to the Earth's rotation, the acceleration due to gravity (g) is minimum at:

A. The Equator

B. The North Pole

C. The South Pole

D. A latitude of 45 degrees

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Correct Answer: Option A

Explanation:
The effective acceleration due to gravity at latitude lambda is g' = g - R * w^2 * cos^2(lambda), where w is angular velocity. At the equator, lambda = 0, so cos(0) = 1. This subtracts the maximum outward centrifugal acceleration (Rw^2) from g. At the poles, lambda = 90, centrifugal effect is zero. Thus, g is minimum exactly at the equator.

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Question #3

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A seismograph is used to detect:

A. Sound waves in water

B. Earthquakes

C. Atmospheric pressure changes

D. Magnetic field variations

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Correct Answer: Option B

Explanation:
Seismograph detects and records ground motions caused by earthquakes, volcanic activity, or explosions. It measures seismic waves (P-waves, S-waves). Barometer detects pressure changes; hydrophone detects underwater sound; magnetometer detects magnetic fields. Memory tip: 'Seismo = earthquake (like seismology)'. This instrument-application question tests knowledge of geophysical tools, frequently examined in competitive exams. Always associate instrument names with their field of use: seismograph (geology), barometer (meteorology), etc.

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