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hamo210 · May 23, 2009, 05:43 AM

First question :The unit of measurement of the electric charge is :
1)kg m^2sec^-2 volt^-1 2)volt sec^-1ohm^-1 3)watt volt^-1sec^-1
Second question:
A ball with 200 gm of mass falls of an altitude of 2 meters towards the ground , because of the non elastic chock with the ground , the ball lost 25% of its energy. Find the maximum reached altitude of the ball when it rebounds up .
Third question:
Two lamps with resistance of 1 ohm and 4 ohm are connected in series with a battery of 10 volts.Find the needed resistance to be connected in order that the consumed potency becomes one third the consumed potency before adding the resistance.

Unknown008 · May 23, 2009, 12:37 PM

1. Use your formulae:

$Q=It$ where Q is charge, I is current, and t is time and;

$V=IR$ where V is voltage, I is current and R is resistance.

2. Find the potential of the ball, through $E_p=mgh$ , where E is potential energy, m is the mass of the ball, g the acceleration due to gravity and h the altitude.

Then, find 25% of that energy.

Finally, through $E_p=mgh$ again, find h, with the new value of Ep you just found.

3. Find the total resistance in series, through $R_1 + R_2 = R_T$

If you want to reduce the amount of voltage consumed, you'll have to decrease the resistance. This is done by connecting a resistor in parallel. I assume you know your formula to find the total resistance of resistors in parallel. You then equate the total resistance to 1/3 of what you've got initially to find the resistance you need to introduce.

Hope it helped! :) Post back if you want more details, but try on your own first, k? :)