physics
posted by Keith .
a girl throws a ball vertically upwards at 5m/s from the roof of a building 20m high
how long will it take the ball to reach the ground? and what will its speed be when it strikes the ground

when at the top, vertical velocity is zero
vf=0=vi+gt solve for t, time to top.
How long it will take to get to the ground?
Hf=Hi+vi*t1/2 g t^2 hi=20, hf=0, solve for t to get time in the air. 
T=1.2
Respond to this Question
Similar Questions

physics
A 3.00 kg ball is dropped from the roof of a building 176.4 m high. While the ball is falling to Earth, a horizontal wind exerts a constant force of 12.0 N on it. a.)How far from the building does the ball hit the ground? 
physics, please help me, this question is hard
John Stands at the edge of a flat roof of a three story building and throws a 180g ball straight up into the air that reaches a height of 3.0 meters above the roof. ( building is 14 meters high) A. What is the initial speed of the … 
11 Physics
my teacher gave me this question for review and i don't know how to do it!! HELP!!! A ball is thrown upwards, from a building. It's height(h), in meters above the ground seconds(t) after being thrown is given by h(t)=5t^2+15t+50 a) … 
Physics
A ball is thrown upwards, from a building. It's height(h), in meters above the ground seconds(t) after being thrown is given by h(t)=5t^2+15t+50 a) How tall is the building? 
Physics
Carlos is in an roof of a building of 20 meters tall, he throws a tennis ball vertically upwards at 15 m/s velocity after it reaches its highest height, the ball goes down until it reaches the ground (see the figure). Based on this … 
Physics
Carlos is in an roof of a building of 20 meters tall, he throws a tennis ball vertically upwards at 15 m/s velocity after it reaches its highest height, the ball goes down until it reaches the ground (see the figure). Based on this … 
physcis
a girl throws a ball vertically upward with a speed of 20 ft/sec from the roof of a building 60 ft high.(a)how long will it take the ball to reach the ground? 
Physics
Two students are on a balcony a distance h above the S street. One student throws a ball vertically downward at a speed vi ; at the same time, the other student throws a ball vertically upward at the same speed. Answer the following … 
Physics
A ball is thrown horizontally from the building roof at a speed of 20 m/s. Takes ball 4 seconds to reach the ground. How tall is building? 
Physics
A girl throws a ball vertically upwards at 10m/s from the roof of a building 20m high. How long will it take the ball to reach the ground?