space dot point (1 Viewer)

[ontherun]

perform a first hand investigation, gather information and analyse data to calculate initial and final velocity, maximum height reached, range and time flight of a projectile for a range of situations by using simulations, data loggers and computer analysis.

CAN SUM! PLZ GIVE ME A COMPLETE ANSWER OR DIRECT ME TO SUM SITE THAT HAS ALL THE RIGHT INFO?

 

[zeropoint]

perform a first hand investigation, gather information and analyse data to calculate initial and final velocity, maximum height reached, range and time flight of a projectile for a range of situations by using simulations, data loggers and computer analysis.

CAN SUM! PLZ GIVE ME A COMPLETE ANSWER OR DIRECT ME TO SUM SITE THAT HAS ALL THE RIGHT INFO?

Use a data logger connected to computer interface to measure the position of a basketball at various timesteps as it rolls off the edge of a table. The range x of the basketball and the height h of the table can be determined using a standard metre rule. The fall time can be measured using a stopwatch. Perform multiple trials to gather the results for various velocities and constant fall times. Analyse the results by computing the slope of the ball's worldline to determine the initial horizontal velocity u and the average fall time . Compare this time to the theoretical value determined using h = 4.9t^2. Perform linear least squares regression of range on initial velocity to obtain another estimation of the fall time. You could also use different values of h and t to estimate the acceleration due to gravity.

 

[CrashOveride]

Sorry didnt feel like creating new thread just a quick question:

for gravitational potential energy, its 0 at infinity and lowest at surface of the planet. so to move an object from infinity to soem distance closer to say Earth is going to take less work to move it over this larger distance than to a point halfway between Earth and infinty. Is that because when you get closer the GPE is tranforming into kinetic energy and speeds up due to gravittatonl attraction ...or whats the proper reasoning here ?

 

[helper]

Not quite what your trying to say.

If you gravity moves an object from infinity to the earth's surface, then it will do more work than if it moves it from infinity to half way.

 

[CrashOveride]

But we have said that its the least GPE at the surface of the earth...and it grows larger as it approaches infinity....so using the definition of GPE as the work done to move an object from infinty to a point in the field, what do you make of it now ? Im a bit confused.

 

[helper]

Are you talking about you doing work against gravity, or gravity doing the work?

You doing work (or rocket) against gravity. It will require you to do more work to move from the surface of the Earth to infinity than from the surface to halfway.

The largest it can reach is 0. At any point closer than infinity it is negative. So you are increasing the amount of GPE from less than zero to zero.

If gravity is doing the work it is reducing the GPE from to zero to less than zero.

 

[CrashOveride]

ok so if gravity was doing the work, then as it moves the objkect closer to some planet or Earth the GPE is decreasing, as its 0 at infinty and negative before that. So looking from ininfinty, the GPE of some object towards the earth is getting less and less as we appraoch the earth. Usinng the definition of GPE as the work done to move the object from infinity to a point in the gravitational field, then because GPE is decreasing as we get closer the work done is decreasing as we get closer? So you need less work to go the further distance...which is illogical so im trying to see where im wrong ?

 

[helper]

Work is the change in GPE

W = GPE final - initial
= a negative number indicating that the GPE is decreasing as it is converted to KE, however the magnitude of the work is getting greater. So the amount of work is greater.

Don't confuse the negative as being magnitude.

 

[gordo]

since a gravitiational froce exists as long as 2 masses exist and have a displacement and the equation has r^2 on the bottom, then u let when r = infinite f = 0. i.e. 0 gravitional energy at infinite distance away (hypothetical of course) so thats your 0 point
if an object is within the gravitational field of another, then moving it closer to the object will increase the force, since the demoninator becomes less, therefore as u move away from the object the force becomes less.
since it would be impossible to define the maximum gravitiational potential energy, since this owuld be when r = 0 and r is the denominator, hence undefined, we let the maximum be 0 when r is inifnite and then make the number larger as it appraoches zero. therefore the gravitational energy must be a negative number apparoahcing zero as r tends to infinite.

hope that helped

 

[CrashOveride]

ok because one dot point says that a change in GPE is related to wokr done while the other says GPE is the work done to move an object from a very large distance away to a point in the grav. field.

One says CHANGE while the other says IT IS. It's not contradictory ?

 

[helper]

The two agree.

Work done = change in GPE
As infinity is zero, the GPE at a point is equal to the change, as zero will not exist in formula

 

[CrashOveride]

Ah ok thanks helper

 

[CrashOveride]

another thing, how did belief in the aether pose a problem for the principle of relativity?

It states here:

"However, belief in the aether posed a difficult problem for the principle of relaitivty, because the aether was supposed to be stationary in space, and light was supposed to have a fixed velocity relative to the aether. Thus, an optical experiment whereby the speed of light is measured provides a way to violate the principle of realitivty."

How does it violate?

 

[mojako]

another thing, how did belief in the aether pose a problem for the principle of relativity?

It states here:

"However, belief in the aether posed a difficult problem for the principle of relaitivty, because the aether was supposed to be stationary in space, and light was supposed to have a fixed velocity relative to the aether. Thus, an optical experiment whereby the speed of light is measured provides a way to violate the principle of realitivty."

How does it violate?

because.. because...
it is predicted that that quote is from Jacaranda,
and it is known by the principle of mathematical induction that somewhere before that the book says something about how we can't show whether an inertial frame of reference (frame of reference which is not accelerating) is moving or not, without looking from outside that frame.
but.. but... conclusion can be drawn using the third step of mathematical induction that since light is supposed to travel at fixed velocity relative to the stationary aether when n=1, and since S(k) true implies S(k+1) true, and since the quote from Jacaranda is somewhat distorted in the process of typing due to natural decay, if from the earth we can detect a difference in the speed of light when it travels in a certain direction, we can detect that the earth is moving in space. Hence by proof of contradiction, S(n) can't be true for al n. Hence, the principal of relativity is violated.

 

[Jase]

Mojako mate... too much 4U!

But yes, barring all the induction... that's about right.
The fundamental principle of relativity (that's newtonian relativity) states that an observer travelling in an inertial frame cannot tell whether they are moving with uniform velocity or not. or no mechanical experiment can determine any difference between any two inertial frames.
If you can measure the relative speed of light in the Aether, then that means you can tell whether your moving or not. Which violates above principle.

 

[mojako]

Mojako mate... too much 4U!

oh not really.
we were playing a kind of induction game last night and I'm just annoying Mr CrashOveride.

but of course this induction game involved no maths at all.

 

[CrashOveride]

If you can measure the relative speed of light in the Aether, then that means you can tell whether your moving or not. Which violates above principle.

thats basically what my question comes down to. how does that work =p

and also, principle of relativity was originally put forward by Galileo so the einstein special relativity is just the addition that the constancy of the speed of light?

 

[mojako]

and also, principle of relativity was originally put forward by Galileo so the einstein special relativity is just the addition that the constancy of the speed of light?

umm.. you mean, 1+1=2?
intriguing...

stop messing someone else's thread.... =p

 

[Constip8edSkunk]

galilean relativity took time to be constant and velocity of all things to be variable
einstein's relativity took velocity of light to be a const. and the others stuff to be variable

so yeah a bit of an adjustment to the same idea