# The following which is the most likely torque

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8. Of the following which is the most likely torque supplied by friction? (A) -0.06 Nm (B) -0.10 Nm (C) +0.06 Nm (D) +0.10 Nm
9. Two disks rotating in the same direction about the same axis are shown above. The rotational inertia for each disk is the same, that is I1= I2 = I. The initial angular speeds are ω1and ω2ω2= 3ω1. If the two disks slide along the axis, collide and stick together, which of the following statement will be the correct expression for the rotational kinetic energy of the combined disk? 10. An 80 cm long non-uniform stick has two masses, 200 g and 225 g hanging on its ends. The stick itself has a mass of 200 g. The system is balanced at the point P exactly half way between the ends of the stick. Which of the following is the distance of the center of mass of the stick from its left end? where
AP PHYSICS ELECTRICITY Charge is Conserved: Charges cannot be created or destroyed. Like charges repel, unlike charges attract Coulomb’s Law Similar to universal gravitation law Electric force: 122k q qFr=UNITS of charge C (Coulombs) ris not a radius, it is the separation between the charges. Current: The flow of electricity. Current I is considered positive (due to old convention). We now know that the electrons flow, but think of current as positive.qItΔ=UNITS: A (Amps) Electromotive Force: emf.Not really a force. In an open circuit the rating of a battery is equal to the emf. When a circuit is closed the potential difference across the battery is slightly less than the emf because of the internal resistance of the battery. The symbol εmight show up to indicate the potential difference or voltage of an ideal battery. Potential Difference: Also called voltage. It is the energy per unit charge provided by the battery. UNITS: V (volts) Resistance: When water flows down a stream it runs into resistance, such as rocks and sand, etc. When current flows in a length of wire, internal properties of the wire slows the current. Resistance is like friction countering the forward progress of the electrons. Resistance is a function of resistivity, ρ, wire length L , and cross sectional area A. LRAρ=UNITS: Ω(ohms) Ohm’s Law:The current is directly proportional to the potential difference and inversely proportional to the resistance VIR=If an element in a circuit is ‘ohmic’ (follows Ohm’s Law) the graph of potential difference versus current is a straight linewhose slopeis the resistance. Electric Power: PVI=UNITS: W (watts) The brightness of lightbulbs depends on power. Ammeter:Measures current or flow of electrons througha wire. Should always be placed in series.Voltmeter:Measures potential difference across an element (resistor, lightbulb). Should always be placed in parallel. Series Circuit Current stays the same 123totalIIII===Voltage adds up 123batteryVVVV=++Equivalent Resistance 123SRRRR=++Parallel Circuit Current adds up 123totalIIII=++Voltage stays the same 123batteryVVVV===Equivalent Resistance 1231111PRRRR=++KIRCHHOFF’S RULES RULE 1.Conservation of Charge
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