Solution :
Given
Diameter of the roulette ball = 30 cm
The speed ball spun at the beginning = 150 rpm
The speed of the ball during a period of 5 seconds = 60 rpm
Therefore, change of speed in 5 seconds = 150 - 60
= 90 rpm
Therefore,
90 revolutions in 1 minute
or In 1 minute the ball revolves 90 times
i.e. 1 min = 90 rev
60 sec = 90 rev
1 sec = 90/ 60 rec
5 sec = 
= 75 rev
Therefore, the ball made 75 revolutions during the 5 seconds.
That's the 'electrostatic' force.
I think it's The fossil record. The same animal fossil is in Africa and South America. The animal could have not swim across so its the fossil record
APPARENT MOTION- <span>the sensation of seeing movement when nothing actually moves in the environment, as when two neighbouring lights are switched on and off in rapid <span>succession.</span></span>