Math

posted by .

A stone is thrown vertically upwards from a platform 60meters above the ground. The initial velocity of the stone is 20m/s.The height of the stone above the ground at t seconds is given by: H(t)=20t-5t^2+60m.How long does it take for the stone to hit the ground? At what velocity does the stone hit the ground?

• Math -

what does it mean when it hits the ground? height H(t) = 0. so, since

H(t) = -5t^2 + 20t + 60
= -5(t^2 - 4 - 12)
= -5(t-6)(t+2)

when do you think it hits the ground?

Then, since

V(t) = 20 - 10t

you can figure the velocity

Similar Questions

1. Uniswa

A stone thrown from the top of a building which is 30m is given an initial velocity 20m/s verticaly upward.the stone misses the edge of the building on its way down. A,what is the velocity of the stone after 1second,n after 3seconds. …
2. calc

a stone is thrown striaght up from the roof of an 80 foot building. the height of the stone above the ground t seconds later is giving by the function h(t)=-16t^2 + 64t +80 during what time is the stone rising?
3. Dynamics

A stone is thrown vertically upward from the top of a 30m high building with a velocity of 15m/s. Taking the acceleration of stone as 9.81 m/s2. And taking that as constant, determine a) the velocity v and elevations sy of stone above …
4. Dynamics

A stone is thrown vertically upward from the top of a 30m high building with a velocity of 15m/s. Taking the acceleration of stone as 9.81 m/s2. And taking that as constant, determine a) the velocity v and elevations sy of stone above …
5. science

a stone is thrown vertically upwards fron the edge of a cliff of height 100m, with a velocity of 9m/s. The stone then fall to the ground(the foot of the cluff). Determine the total time the stone will take to hit the ground
6. Physics

A stone is thrown up vertically from the ground (the gravitational acceleration is g = 10 m/s^2 ). After a time dt =1 s, a second stone is thrown up vertically. The first stone has an initial speed v1 = 11.0 m/s, and the second stone …
7. Physics

A stone A is dropped from the top of a very high platform. At the same time another stone is thrown vertically upward from the ground level with an initial speed of 50m/s. At the instance that the stone passes each other, the ration …
8. Physics

A stone is thrown from the top of a tower of height 60m with velocity 40m/s at an angle of 30 degree above the horizontal. Calculatethe time taken by the stone to hit the ground. At what distance from the foot of the tower the stone …
9. physics

A hoodlum throws a stone vertically downward with an initial speed v0 from the roof of a building, a height h above the ground. (a) How long does it take the stone to reach the ground?
10. physics

A hoodlum throws a stone vertically downward with an initial speed v0 from the roof of a building, a height h above the ground. (a) How long does it take the stone to reach the ground?

More Similar Questions