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A stone is dropped from the roof of a tall building. A person measures the speed of the stone to be 49 m/sec when it hits the ground. The height of the building is closest to:
Select one:
a. 24 meters.
b. 49 meters.
c. 122 meters.
d. 245 meters.
 one year ago
 one year ago
A stone is dropped from the roof of a tall building. A person measures the speed of the stone to be 49 m/sec when it hits the ground. The height of the building is closest to: Select one: a. 24 meters. b. 49 meters. c. 122 meters. d. 245 meters.
 one year ago
 one year ago

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DecartBest ResponseYou've already chosen the best response.2
\[mgh = \frac{ 1 }{ 2 }mv ^{2}\]
 one year ago

DecartBest ResponseYou've already chosen the best response.2
you can subtract the mass from both sides which shows that everything falls at the same rate
 one year ago

DecartBest ResponseYou've already chosen the best response.2
so if you plug in the velovity and solve for h which is the height
 one year ago

DecartBest ResponseYou've already chosen the best response.2
is this for conservation of energy
 one year ago

omnomnomBest ResponseYou've already chosen the best response.0
No this is only for the height of the building
 one year ago

DecartBest ResponseYou've already chosen the best response.2
The formula I gave you is the conservation of energy
 one year ago

wioBest ResponseYou've already chosen the best response.0
In this case \(g\) is the gravitational acceleration we talked about in the previous problem.
 one year ago

DecartBest ResponseYou've already chosen the best response.2
You cannot solve this with kinematics there are too many unknowns
 one year ago

wioBest ResponseYou've already chosen the best response.0
What do you mean you can't solve it with kinematics?
 one year ago

DecartBest ResponseYou've already chosen the best response.2
Yeah I guess you could solve for time in the acceleration then plug it in the average velocity.
 one year ago

wioBest ResponseYou've already chosen the best response.0
I was talking about the \(g\) in your formula.
 one year ago

wioBest ResponseYou've already chosen the best response.0
Though technically speaking, depending on whether they are on the 'energy' part or the 'kinematic' part of the course decides which method they should use.
 one year ago

DecartBest ResponseYou've already chosen the best response.2
that is why I was asking
 one year ago

wioBest ResponseYou've already chosen the best response.0
Last question was a 'kinematic' one so maybe it must be kinematics.
 one year ago

DecartBest ResponseYou've already chosen the best response.2
acceleration of gravity = velocity final minus velocity inital divided by time.
 one year ago

wioBest ResponseYou've already chosen the best response.0
@omnomnom Have you talked about work or energy in your class yet?
 one year ago

wioBest ResponseYou've already chosen the best response.0
Like potential energy or kinetic energy?
 one year ago

wioBest ResponseYou've already chosen the best response.0
It is something you will learn in the future, most likely.
 one year ago

DecartBest ResponseYou've already chosen the best response.2
yes solve for time then plug into \[\frac{ d }{ t }=\frac{ v _{f}+v _{i} }{ 2 }\]
 one year ago

DecartBest ResponseYou've already chosen the best response.2
conservation is so much easier to solve
 one year ago

omnomnomBest ResponseYou've already chosen the best response.0
it confused me though the first equstion
 one year ago

wioBest ResponseYou've already chosen the best response.0
@omnomnom This is a two step problem. First you want to figure out how long it took to fall. Then you want to use that to figure out how far it fell.
 one year ago

omnomnomBest ResponseYou've already chosen the best response.0
oh okay so what equation do i use.... is is\[d =Vi( t)+ a \frac{ 1 }{ 2 }(t^2) \]
 one year ago

wioBest ResponseYou've already chosen the best response.0
You can't use that equation until you find time though.
 one year ago

DecartBest ResponseYou've already chosen the best response.2
\[a=\frac{ v _{f}v _{i} }{ t }\]
 one year ago

DecartBest ResponseYou've already chosen the best response.2
you know a and both velocities
 one year ago

omnomnomBest ResponseYou've already chosen the best response.0
But we need the time :( Cant i just quess the answer?
 one year ago

wioBest ResponseYou've already chosen the best response.0
Yes, \(a\) is the same as last time... \(9.81m/s^2\)
 one year ago

wioBest ResponseYou've already chosen the best response.0
You are not supposed to guess, because there is already a way to find the answer.
 one year ago

omnomnomBest ResponseYou've already chosen the best response.0
but...... Whats the way ?
 one year ago

DecartBest ResponseYou've already chosen the best response.2
then plug in the time into your equation and find x
 one year ago

omnomnomBest ResponseYou've already chosen the best response.0
so we change the equation now?
 one year ago

DecartBest ResponseYou've already chosen the best response.2
you want the height of the building
 one year ago

DecartBest ResponseYou've already chosen the best response.2
do you understand the kinematic equations
 one year ago

omnomnomBest ResponseYou've already chosen the best response.0
The first one ? NO the others Yes
 one year ago

DecartBest ResponseYou've already chosen the best response.2
http://www.physicsclassroom.com/
 one year ago

DecartBest ResponseYou've already chosen the best response.2
this is a helpfull tool
 one year ago
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