pendulum logic help

[pizza1994]

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Can someone explain the following two:

1) If the gravitational pull on a pendulum is stronger then the pendulum will move faster

2) If the pendulum has a higher initial height then is moves faster

I dont get it. if you have a higher gravitational pull then that means you are more "attracted" to Earth right? and b/c you experience this larger attraction force then I would think that the pendulum should move slower b/c its more "constrained due to attraction." I dont know.

and for inital height I just dont get the logic

 

[DrknoSDN]

2) assuming the pendulum is not extremely long or shaped strangely it will be at less than terminal velocity so it should continue to accelerate throughout the fall gaining more velocity if it started higher.

1) Changing (increasing) gravity will exert a larger force on the same size mass (pendulum bob), so the acceleration will be larger. If the pendulum falls over a distance X, but experiences a larger acceleration then the maximum velocity when it reaches minimum height (all PE -> KE) will be increased.

 

[pizza1994]

2) assuming the pendulum is not extremely long or shaped strangely it will be at less than terminal velocity so it should continue to accelerate throughout the fall gaining more velocity if it started higher.

1) Changing (increasing) gravity will exert a larger force on the same size mass (pendulum bob), so the acceleration will be larger. If the pendulum falls over a distance X, but experiences a larger acceleration then the maximum velocity when it reaches minimum height (all PE -> KE) will be increased.

when a pendulum "starts higher" does that mean your angle of theta is closer to 180?

 

[Cawolf]

Yes the angle would be closer to 180 for it to start higher.

 

[DrknoSDN]

Normally you think of a pendulum maximum as 90 degrees because you get strange behavior beyond that. Here however you would get a faster swing all the way up to almost 180 (assuming it is not balancing inverted)

They just meant a "higher height" is a greater distance from maximum height (All PE) to minimum height (All KE). Changing the length of the arm/string is the easiest way to do that and stay under 90 degrees.

 

[pizza1994]

2) assuming the pendulum is not extremely long or shaped strangely it will be at less than terminal velocity so it should continue to accelerate throughout the fall gaining more velocity if it started higher.

1) Changing (increasing) gravity will exert a larger force on the same size mass (pendulum bob), so the acceleration will be larger. If the pendulum falls over a distance X, but experiences a larger acceleration then the maximum velocity when it reaches minimum height (all PE -> KE) will be increased.

so for number 1 can I think of it like this:

larger g means smaller T (period) and smaller T means larger frequnecy and hence larger frequency means larger velocity b/c of v= lambda * f? is this right?