A small bag of sand is released from an ascending hot-air balloon whose upward constant velocity is v0 = 1.45 m/s. Knowing that at the time of the release the balloon was 70.3 m above the ground, determine the time, τ, it takes the bag to reach the ground from the moment of its release.

Answer 1

Well you need to use the equations of motion

v=u+at
v^2=u^2+2aS and
S=ut+(1/2)at^2

a = -g in this question

What happens first is the bag moves upwards for a short time (as it has a velocity of 1.45m/s) and then falls down

You can do this question in one go (instead of working out how long it takes to go up and then how long it takes to fall down and add the two)

Use the following
u (initial velocity) = 1.45m/s
S (displacement) = -70.3m
a (acceleration) = -g = -9.8m/s

Use those to find t using the equations above (you need only 1 of them)