A few days ago
Somebody

# Can anyone help?

A ball is thrown upward from the roof of a building 100 m tall with an initial velocity

of 20 m/s.

When will the ball reach a height of 80 m?

A few days ago
lilkrazyme3

i think it is 3s…

h=20t-10t^2

h=10t(2-t)

t=0 t=2

it goes up for 2 seconds(40m)

140-80= 60 divided by 20 is 3..

0

A few days ago
original_pet
I can’t answer this question but I will tell you one thing, it isn’t 4 seconds.

If you start at 100 meters then throw the ball upwards, it has to go up a while, then back down. The ball will have to travel at some type of angle so it doesn’t hit the building again… but what angle will you throw it at? You have to know the angle the ball was thrown. In addition, I think you also have to know how heavy the ball is… a tennis ball travels a lot higher than a bowling ball when they are both thrown upwards at 20 meters per second.

0

A few days ago
LBRINDLEY
first determine when at what height the ball will reach 0 m/s

then take that height factor gravity as acceleration till the ball drops to 80 so 100+height ball was when started to fall +20=total distance

0

A few days ago
Anonymous
4 seconds
0

A few days ago
susan s
100 m

20m per second

5 seconds to reach 100m

therefore 4 seconds x 20m equals 80m.

0