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Physics: Post your doubts here!

Thought blocker

Thought blocker

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7)
Its D read your book properly, its mentioned :p
9)
For projectile motion, the vertical acceleration is the same throughout and is equal to g. There is no component of acceleration in the horizontal direction, so horizontal velocity is unchanged. But vertical speed changes due to which the resultant velocity changes.
10)
This is given in book as well :) Force is the rate of change of momentum :)
31)
Its D, same book dekho :)
34)
img-20121122-00179-jpg.18658
 
A

adarsha

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Physicist said:
before going on, you should check if you have included all information and if question is typed correctly

Solution:
Force, F is equal to rate of change of momentum. (F = Δp / t)

Force is also equal to ma and momentum is given by p = mv (assuming the ball is at rest initially)

So, ma = mv / t giving a = v / t = 70 / 0.0005 = 140 000

but this answer is not realistic. you should check the question again

By the way, you should also try to visit the link in my signature, it should help
Click to expand...

the question is same and that's all the information that is given to me, but i was able to find the answer when i used "velocity * weight * 2" . is it anyway possible that the formula used would be correct?? thanks i will check your blog. :)
 
princess Anu

princess Anu

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Please tell me the method to solve these questions
1, A load of 10kg is hung using two strings 9m and 12m long tied to two points at the same level 15 m apart. Find the tension in each string? Ans: 58.8
2, A mass of 2kg is in equilibrium on a smooth plane inclined at an angle of 30 to the horizontal. Find
(i) the minimum force required so that the mass is in equilibrium,
(ii) The normal reaction force on the mass by the plane
 
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adarsha

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Muskan Achhpilia

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Thought blocker said:
Well I solved all of them and found that one of your answer is wrong. That is of kinetic energy.
So Here you go :
15)
So Clock wise moment = Anti Clock wise moment
Therefore 300 * 0.4 = 200 * 0.8
--> 40 Anticlockwise direction.
Alternative :
By taking the torque clockwise at the centre:-
=>300 x 0.4 - 200 x 0.4 = 40 Nm (clockwise)
=>Thus to balance it required torque is 40 Nm (anticlockwise)
=>(B)

13)
Already answer. Here in some more detail,
The ratio of the radius of the pulley to the arm is 0.2m/0.6m. Multiplying that by 900N gives you 300N. There are two force vectors, so 150N needs to be applied to each arm.
In other words,
To lift the weight, the cord needs to exert at least 900 N of force.
This means the disc needs to exert at least (900 N * 0.20 m) of torque.
This means the two forces on the lever needs to each exert at least (1/2 * 900 N * 0.20 m) of torque.
This means each force on the lever needs to be at least (1/2 * 900 N * 0.20 m / 0.60 m).
-> 150N

10)
This is the question where ms might not be correct or you haven't looked properly,
X = 1/2 x m x (-v)^2
Y = 1/2 x 2m x v^2 = m x v^2
Ratio of X/Y :
1/2 x m x v^2
--------------- = 1 / 2
m x v^2

Hope you got all of them. :)
Click to expand...

Checked xtremepapers after ages, Thanks a tonne!!!:)
 
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