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7 answers

u=?,v=0,a=-10m/s^2, S=80m
Use 2aS=v^2-u^2
2*(-10)S=0-u^2
u^2=2*10*80
u^2=1600
u=40m/s. ANS.

2007-08-27 08:58:38 · answer #1 · answered by Anonymous · 2 0

Ignoring air resistance, this is exactly the same as asking "If a ball is dropped from 80m, how fast will it be going as it hits the ground?" (which is exactly what happens after the ball begins to drop again to complete its trip in the air.

Ballistic equation (initial velocity=0) is
x = 0.5*a*t^2 where a = g = 9.81m/(s^2) and x = 80m

80m = 0.5*9.81 * t^2
solving for t: t=4.04 seconds

V(t) = a * t = g* t = 9.81m/s^2 * t
V(4.04sec) = 39.84 m/s (meters per second)

2007-08-27 09:15:32 · answer #2 · answered by tinfoil666 3 · 0 0

Assuming there's no air resistance, you need to throw it at a speed such that its initial kinetic energy exactly matches the final potential energy of the ball at a height of 80 m.

Kinetic energy = Potential energy
KE = PE
1/2*m*v^2 = m*g*h
1/2*v^2 = g*h
v^2 = 2*g*h
v = sqrt(2*g*h)
v = sqrt(2*(9.81 m/s^2)*(80 m))
v = 39.62 m/s

You need to throw the ball with an initial vertical velocity of 39.62 m/s.

2007-08-27 09:02:36 · answer #3 · answered by lithiumdeuteride 7 · 0 0

human beings make it so perplexing. Its effortless. Kinetic capability at launch = ability capability at max top. So a million/2 mv^2 = mgh m cancels - so which you do not could desire to be responsive to it in any respect v = sqrt (2gh) = sqrt (2.10.eighty) = sqrt 1600 = 40 m/s

2016-10-03 07:46:01 · answer #4 · answered by ? 4 · 0 0

kinetic energy given= potential energy of 80 metre
1\2mv2=m*g(10)*80
v=1600root=40m\s

2007-08-27 08:59:42 · answer #5 · answered by KESHAV G 1 · 0 0

Maximum height: v=at

a=gravity=9.8m/s^2

Distance formula:
d=vt-0.5at^2
80=[(9.8)*t]*t-0.5*9.8*t^2
80=9.8t^2-4.9t^2
80=4.9t^2
t=sqrt(80/4.9)
=4.04seconds

v=9.8*4.04
=39.592 m/s

2007-08-27 08:59:14 · answer #6 · answered by active open programming 6 · 0 0

i can guess the answer
40m/sec because v(square)=2gh where g=10m/sec square.
i hope it shd be correct.

2007-08-27 09:03:51 · answer #7 · answered by ritika 2 · 0 0

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