Question

18. A coin is placed on a gramophone record rotating at a speed 45 rpm. It files away
when the rotational speed is 50 rpm. It two such coins are placed over the other on
the same record, both of them will fly away when rotational speed
1) 100 rpm
3) 12.5 rpm
2) 25 rpm
4) 50 rpm

19. A car is moving with speed 30 m/s on a circular path of radius 500 m. Its speed is
increasing at the rate of 2 m/s? What is the acceleration of the car
1) 2ms
2) 2.7m/s
3) 1.8ms
4) 9.8m/s

20. A motor car with a mass m moves with a uniform speed v on a
(i) horizontal level bridge
(ii) convex bridge
(iii) concave bridge
The force exerted by the motor car when it is at the centre of the bridge, is
1) Highest in case (i)
2) Highest in case (ii)
3) Highest in case (iii)
4) same in the three cases

21. The angular speed of a car increase from 600 rpm to 1200 rpm in 10 sec. What is
the angular acceleration of the car ?
1) 600 rad/s²
2) 60 rad/s²
3) 60 πrad/s²
4) 2 πrad/s²​

Answer 1

21 1200-600/10 = 60rad/s2

Answer 2

Answer:

100 rpm

9.8 ms

highest in case second

60

Explanation:

hope this may be helpfull