Basic Physics

# Uniform motion in a horizontal circle – problems and solutions

1. A 0.2-kg ball, attached to the end of a horizontal cord, is revolved in a circle of radius 1 meter and ball’s maximum speed is 10 rpm. What is the magnitude of the centripetal acceleration and the magnitude of the tension force?

Known :

Mass (m) = 0.2 kg

= 10 rev/min = 10 rev/60 s = 0.17 rev/s = (0.17)(6.28 rad)/s = 1 rad/s

Velocity (v) = r ω = (1 m)(1 rad/s) = 1 m/s

Wanted : as dan ΣF

Solution :

(a) The magnitude of the centripetal acceleration (b) The magnitude of the tension force

ΣF = m a

T = m as

T = (0.2 kg)(1 m/s2)

T = 0.2 kg m/s2

T = 0.2 N

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2. A 1-kg ball at the end of a string is revolving uniformly in a horizontal circle of radius 1 m. The cord will break when the tension in it exceeds 100 N. What is the maximum speed the ball can have?

Known : Mass (m) = 1 kg

Tension force (T) = centripetal force (ΣF) = 100 N

Wanted: v maximum

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