A 35 g steel ball is held by a ceiling-mounted electromagnet 3.5 m above the floor. A compressed-air cannon sits on the floor, 4.0 m to one side of the point directly under the ball. When a button is pressed, the ball drops and, simultaneously, the cannon fires a 25 g plastic ball. The two balls collide 1.0 m above the floor. What was the launch speed of the plastic ball

8.95 m/s

Explanation:

(3.5-1.0) x 2 = gt²

t = √5/9.8 = 0.714 sec  

= X/t = 4/ 0.714 = 5.602 m/s

vertical velocity means it has to rise 1.0 m against gravity in 0.714s

= gt = 9.8 x 0.714 = 6.99 m/s

V = √²+ ² = √6.99²+5.602² = 8.95 m/s

i think it is non rem sleep

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.