physics 2 anyone help? What is the maximum torque on a molecule of HCl (dipole moment p = 3.60×10-30 C* m)?
What is the maximum torque on a molecule of HCl (dipole moment p = 3.60×10-30 C* m) in a region of electric field E = 3.1×104 N/C? (N*m)
part 2
A molecule of HCl (dipole moment p = 3.60×10-30 C* m) and moment of inertia of 2.70×10-47* kg m2) is suddenly subjected to an electric field E at right angles to the direction of the molecule's dipole moment. If the initial angular acceleration of the molecule is 2.93×1021 rad/s2, what is the magnitude of the electric field?
could you please tell me how to do it and not just give an answer. thank you
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A dipole is two equal & opposite charges, q, separated by a small distance "L".
The magniyude of the Dipole Moment is
p = qL
It is a vector defined as pointing along "L" from - to +
When placed in an E-field the charges will have equal & opposite forces on them, causing the Dipole to rotate and allign with the E-field.
The equal & opposite forces on the Dipole create a torque "T" which can easily be shown to have the magnitude;
T = pESin@
where the torque can be measured about any axis and where @ is the angle between the p & E vectors.
From inspection, maximum torque occurs when @ = 90 deg and Sin(90)=1
T(max) = pE = (3.6x10^-30)(3.1x10^4) = 11.16 x 10^-26 N-m
2)The law of motion for rotational dynamics is;
Net Torque = (Moment of Inertia) x (angular acceleration)
T = I(aa)
From above, when p & E are at 90deg the torque is pE, so use this for left side;
pE = I(aa)
E = I(aa)/p
= (2.7x10^-47)(2.93x10^21)/(3.6x10^-30)
= 2.2 x 10^4 N/C
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