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Physics: Post your doubts here!

Farheen1201

Farheen1201

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nehaoscar said:
I'm sorry but I don't get it :p
So here's what I think ... please correct me wherever possible
1. The mud is placed on the disc when the disc is stationary
2. The disc starts to move with an increasing angular velocity w (omega)
3. The centripetal force keeps the mud on the disc so it doesn't fly off
4. At the edges the centripetal force is greater than at the center
So I hope these 4 points are correct
Then the centripetal force holds the mud in place so it doesn't fly off right? ...
So if this force is greater, why will the mud fly off when it's role is to hold it in place? :confused:
Click to expand...
The centripetal force increases with increasing radii. The mud on the edge is the farthest away ergo maximum radii. Hence it experiences greatest force and flies of first. The mud on the disc will also fly off but after the mud on the edge has flown off.
 
nehaoscar

nehaoscar

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Physicist said:
teh centripetal does not keep the mud on the disc.

a 'centripetal' force is any force that acts towards the centre. since the mud is on an object in circular motion, it will experience a force.

well, just imagine the real case scenario, the mud would definitely get thrown off.

if anyone else can provide a clearer explanation, you are welcome.
Click to expand...
Ok yeah taking the real case scenario it is clear
But then as you said "a 'centripetal' force is any force that acts towards the centre. since the mud is on an object in circular motion, it will experience a force."
Doesn't that mean the mud will experience a force towards the centre?
 
nehaoscar

nehaoscar

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Farheen1201 said:
The centripetal force increases with increasing radii. The mud on the edge is the farthest away ergo maximum radii. Hence it experiences greatest force and flies of first. The mud on the disc will also fly off but after the mud on the edge has flown off.
Click to expand...
Ok... but is the force the mud experiences the centripetal force?
 
JamesWhite

JamesWhite

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Hi there!

Can anyone explain this question from paper 11 summer of 2015 for me?

A conveyor belt is driven at velocity v by a motor. Sand drops vertically on to the belt at a rate of m kg s^( –1) .
What is the additional power needed to keep the conveyor belt moving at a steady speed when the sand starts to fall on it?
A 0.5mv B mv C 0.5mv^2 D mv ^2

the answer is D.
 
nehaoscar

nehaoscar

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ahmedish said:
Q3 as well??
Click to expand...
First the question says "the pointer does not return fully to zero"
This means that when the current is zero (true value) the scale doesn't show zero.
This tells us that at a true value of 0A, the reading is shown to be more than 0A so it has a + y-intercept
So this means the correct answer is between C and D
Now it also says "meter has become less sensitive at higher currents than it is at lower currents"
less sensetive means that the scale reading would not change as drastically as it did for the lower currents
So the gradient decreases
Therefore the answer is C
 
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