Physics: Post your doubts here!

[_Ahmad]

Can someone plz solve this question... I would really be grateful

 

[immie.rose]

15)
The diving board is in equilibrium - it is not accelerating, it is not revolving.
If an object is not accelerating, there is no net force on the object.
If an object is not rotating, there is no net torque on the object.

The boy is stationary, so the force exerted on him by the board that holds him up is equal in magnitude to his weight. By Newton's Third Law, he exerts the same force downwards on the board. Since his weight is mg, the force he exerts on the board is equal to mg, and acts downwards. This force acts 5.0 meters away from the hinge.

The spring, if deformed by a distance "x", will exert a force of magnitude "kx" upwards on the board. This force contacts and pushes the board 2.0 meters from the hinge.

In this case, we can see that the board isn't rotating, so the net torque on it is zero. So, to find out our answer, we take moments about the hinge:

Moment due to the boy = mg * 5.0 meters = 5mg in the anti-clockwise direction.
Moment due to the spring = kx * 2.0 meters = 2kx in the clockwise direction.

So the net torque is zero, therefore 5mg = 2kx. Therefore, x = 5mg/2k
Putting in the values, we get x = 5 * 50 * 9.81/(2 * 10,000) = 1962/20000 = 0.0981 meters
This is equal to 0.0981 * 100 = 9.81 centimeters = C.

awesome! thanks!

 

[not.maria]

may june 2009 q13
how to solve this?
thanks in advance

 

[Thought blocker]

View attachment 44298
may june 2009 q13
how to solve this?
thanks in advance

see the moment produced by the weight will be
900x0.2=180Nm
the torque by F will be Fx1.2=180
hence F will be 150N

 

[mehria]

ans is D :/

 

[Thought blocker]

View attachment 44302
ans is D :/

Wait I'll come from lapy in 10 mins it's hrad it toye frm cell :/

 

[not.maria]

see the moment produced by the weight will be
900x0.2=180Nm
the torque by F will be Fx1.2=180
hence F will be 150N

why wont we consider the torque of a couple for the weight?
the cord is wound around the disc so wont tension in the cord cause a couple?

 

[mehria]

Wait I'll come from lapy in 10 mins it's hrad it toye frm cell :/

ok

 

[Thought blocker]

ok

Look Proton Has Charge of (+)1.! We need to end Up at One Using Values of Up quark and Down Quark.!

If U Take 2 UpQuarks = (+)(2/3) * 2 = (+)(4/3)
And One Down Quark = (-)(1/3) * 1 = (-)(1/3)
When You add them Together..
(+)(4/3) + (-)(1/3)= (+)1

 

[Thought blocker]

why wont we consider the torque of a couple for the weight?
the cord is wound around the disc so wont tension in the cord cause a couple?

I showed na 180 :/

 

[not.maria]

I showed na 180 :/

but u r multiplying 900 by .2 not .4
wont the tension in the cord cause parallel forces on the disc causing the disc to rotate?

 

[mehria]

Look Proton Has Charge of (+)1.! We need to end Up at One Using Values of Up quark and Down Quark.!

If U Take 2 UpQuarks = (+)(2/3) * 2 = (+)(4/3)
And One Down Quark = (-)(1/3) * 1 = (-)(1/3)
When You add them Together..
(+)(4/3) + (-)(1/3)= (+)1

i didn't get it :/

 

[Thought blocker]

i didn't get it :/

What you dint get in this ?

 

[Thought blocker]

but u r multiplying 900 by .2 not .4
wont the tension in the cord cause parallel forces on the disc causing the disc to rotate?

why you think its 0.4 rather than 0.2?
Well,
no it wont because we are dealing with the minimum force that could lift the weight that is weight=tension, there wont be additional force that could cause the disc to rotate

 

[ShreeyaBeatz]

What does this mean? Please explain. sorry for the two posts. I couldnt remove it

 

[Thought blocker]

i didn't get it :/

Since charge on proton is +ive e, the sum of both 'up quarks' and 'down quarks' should equal to 1.

 

[Thought blocker]

View attachment 44307
What does this mean? Please explain. sorry for the two posts. I couldnt remove it View attachment 44307 View attachment 44307

B ?

 

[ShreeyaBeatz]

B ?

It is C. It seems like A,B and C all seem true

 

[Thought blocker]

It is C. It seems like A,B and C all seem true

Wait ._.

 

[_Ahmad]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w09_qp_12.pdf

Q27,33