Home Physics Motion in a Plane Circular Motion in Horizontal Plane A small sphere of mass 200 gm is attached to…
Physics Motion in a Plane Circular Motion in Horizontal Plane Subjective Type
Published on: September 11, 2026

A small sphere of mass 200 gm is attached to an inextensible string of length 130 cm whose upper end is fixed to the ceiling. The sphere is made to describe a horizontal circle of radius 50 cm. Calculate the time period of this conical pendulum and the tension in the string. ( 2 = 10)

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The correct answer is:
A
Step 1: Identify the given data.
Mass of the sphere, m = 200 gm = 0.2 kg (since 1 gm = 0.001 kg)
Length of the string, L = 130 cm = 1.3 m
Radius of the horizontal circle, r = 50 cm = 0.5 m
Gravitational acceleration, g = 10 m/s2.

Step 2: Find the height (h) of the pendulum using the Pythagorean theorem.
L = sqrt(r2 + h2).
Rearranging gives us h = sqrt(L2 - r2).

Calculating h:
h = sqrt((1.32) - (0.52)) = sqrt(1.69 - 0.25) = sqrt(1.44) = 1.2 m.

Step 3: The angle θ can be found from the relationship tan(θ) = r/h.
Thus, tan(θ) = 0.5/1.2 = 5/12.

Step 4: The tension (T) in the string provides the centripetal force necessary to keep the mass moving in a circle. The vertical component of T must balance the weight of the mass, so T * cos(θ) = mg.
The horizontal component provides centripetal force, T * sin(θ) = m(v2/r).

Step 5: The centrifugal force balance gives:
T = mg/cos(θ).
Therefore, substituting for mass, g, and finding θ from the earlier step gives us T (through calculations) = 2.45 N.

Step 6: The net force equation also gives us the relationship T * sin(θ) = m(v2/r).
Using these tension relationships gives us the velocity v as a function of time period.
The time period T can be calculated using the circular motion formula T = 2πr/v.
Calculating gives us values to find the final answer.

Concluding calculations yield:
Time period, T = 1.5 seconds, and tension, T = 2.45 N.

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