A 1.2-kg mass is projected down a rough circular track (radius = 2.0 m) as shown. The speed of the mass at point A is 3.2 m/s, and at point B, it is 6.0 m/s. What is the change in mechanical energy done on the system between A and B by the force of friction?





a.

?8.9 J



b.

?7.3 J



c.

?8.1 J



d.

?6.6 J



e.

?24 J


c

Physics & Space Science

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A series circuit consists of a 100 V DC power source, a 100 ? resistor, and a variable resistor of resistance R, which varies from 0 to 100 ?. The current in the circuit is



a.
directly proportional to R.

b.
inversely proportional to R.

c.
directly proportional to (100 ? + R).

d.
inversely proportional to (100 ? + R).

e.
neither directly nor inversely proportional to R or to (100 ? + R).

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