You\'re in a glass walled elevator, and it is moving down at a constant speed of

Question

You're in a glass walled elevator, and it is moving down at a constant speed of 2m/s. To pass the time, you bounce a ball off the Boor: You throw the ball down, at a speed of 4m/s, from a height of 1 meter, it bounces off the floor, and you catch it as it comes back up. From your perspective, the ball moves 1 meter down, and it takes 1/4 second to hit the floor. To someone watching from outside, how far doest the ball move, and how long does it take to hit the elevator floor? It moves down 1m and takes .4s it moves down 1.8 m and takes .4s it moves down 1m and takes .25s it moves down the 1.5 m and takes .25s it moves down 3.4m and takes 1.2s none of these choices is correct I push a box max m with force F. it takes me 5 seconds to push it a distance d. My lazy friend pushes the same box with half the force, F/2 how long does it take her to push the same box the same distance? It takes 4 times a s long it takes half as long it takes 2 times as long it takes 2 squareroot 2 times as long none of these choices is correct

Explanation / Answer

(4)
F = m*a
Distance = d
time = 5 s

d = u*t + 1/2* a*t^2
d = 0 + 1/2 * (F/m) * 25
d = 25/2 * F/m

Now,
The Friend pushes with force = F/2
F/2 = m*a
a = F/(2m)

d = 1/2 * a * t^2
25/2 * F/m = 1/2 * F/2m * t^2
25*2 = t^2
t = sqrt(50)
t = 5 * sqrt(2)

So it takes sqrt(2) times long !!

Correct option - (e) None of these options is correct !!

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