Question

Calculate the period in seconds of each of these motions.

(!) A pulse beats 25 times in 15 seconds
(!!) A fan motor turns at 1200 revolution per minute​

Answer 1

Correct option is C)

Initial frequency ν

i

=1200 r.p.m =

60

1200

=20 r.p.s

Initial angular velocity: ω

i

=2πν

i

=2π×20=40π rad/s

Final angular velocity: ω

f

=0

Using, ω

f

2

−ω

i

2

=2αS

∴ 0−(40π)

2

=2(−4)S ⟹S=200π

2

radian

Number of revolutions: N=

2π

200π

2

=100π≈314