The ratio of angular speed of a second-hand to the hour- hand of a watch is

• $\frac{3600}{1}$

• $\frac{720}{1}$

• $\frac{72}{1}$

• $\frac{60}{1}$

82.

Which of the points is likely position of the centre of mass of the system shown in the figure ?

                      

• A

• D

• B

• C

Two balls are thrown simultaneously in air. The acceleration of the centre of mass of the two balls when in air

• is equal to g (acceleration due to gravity)

• depends on the speeds of the two balls

• depends on the masses of the two balls

• depends on the direction of motion of the two balls