A hot-air balloon is rising upward with a constant speed of 2.85 m/s. When the balloon is 2.50 m above the ground, the balloonist accidentally drops a compass over the side of the balloon. How much time elapses before the compass hits the ground

Explanation:

You have to declare which way is plus -- up or down. I will use down.

vi = - 2.85       The balloon is going up. That is the minus direction.

a = 9.81

d =   2.50 meters  distance in this case is from the object to the ground.

d = vi*t + 1/2 a t^2

-2.50 = -2.85*t + 1/2 * 9.81 * t^2

-2.50 = -2.85*t + 4.905 * t^2           transfer the left to the right.

-4.905 t^2 + 2.85*t + 2.50 = 0

Use the quadratic formula to solve for t.

It turns out that t = 1.06

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg