Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa
  • Home
  • NCERT
  • A disc revolves with a speed of 33 1/3 rev/min, and has a radius of 15 cm. Two coins are placed at 4 cm and 14 cm away from the centre of the record. If the co-efficient of friction between the coins and the record is 0.15, which of the coins

Q5.37 A disc revolves with a speed of 33\frac{1}{3}rev/min, and has a radius of 15 cm. Two coins are placed at 4 cm and 14 cm away from the centre of the record. If the coefficient of friction between the coins and the record is 0.15, which of the coins will revolve with the record?

Answers (1)

best_answer

Frequency of revolution is : 

                                                 =\ \frac{100}{ 3\times60}\ =\ \frac{5}{9}\ rev/sec

(i) Case 1 :- When coin is placed at 4 cm :  

                                         Radius  =  0.04 m

                                    Angular frequency : 

                                                                    \omega\ =\ 2 \pi v

or                                                                       =\ 2 \pi \times \frac{5}{9}\ =\ 3.49\ s^{-1}

The frictional force is given by : 

                                                f\ =\ \mu mg 

 or                                                   =\ 0.15\times m\times 10\ =\ 1.5m\ N

Thus the centripetal force will be :

                                               F_c \ =\ mr\omega^2

or                                                    =\ m\times 0.04 (0.39)^2\ =\ 0.49m\ N

Since frictional force is greater than the centripetal force so coin will revolve around the record.

 

(ii) Case 2:-  When the coin is placed at 14 cm  :

                                           Radius  =  0.14  m

The centripetal force will be :

                                               F_c \ =\ mr\omega^2

or                                                    =\ m\times 0.14 (0.39)^2\ =\ 1.7m\ N

Since frictional force is lesser than the centripetal force so the coin will slip from the record.

Posted by

Devendra Khairwa

View full answer

Crack CUET with india's "Best Teachers"

  • HD Video Lectures
  • Unlimited Mock Tests
  • Faculty Support
cuet_ads

Similar Questions

Trending Articles/News

anam-khan

CBSE date sheet 2025 for Classes 10, 12 likely in November last week: Reports
anam-khan

CBSE allows Class 10, 12 students from disaffiliated schools to appear for board exam 2025 from same school
anam-khan

CBSE withdraws affiliation of 21 schools, downgrades 6 schools in two states; most in Delhi

Latest Question