If a space heater consisted of a 10.0 cm radius iron ball through which electrical current was passed in order to heat the ball, what temperature would it need to be raised to in order to radiate 500 W into the surrounding air (which is at a temperature of 
Assume the ball is a perfect blackbody.
A. 510 K
B. 346 K
C. 730 K
D. 530 K
D. 530 K
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A 25-kg block on a horizontal surface is attached to a light spring (force constant = 8.0 kN/m). The block is pulled 10 cm to the right from its equilibrium position and released from rest. When the block has moved 2.0 cm toward its equilibrium position, its kinetic energy is 12 J. What is the change in mechanical energy caused by the frictional force on the block as it moves the 2.0 cm?
A. ?4.0 J B. ?3.5 J C. ?2.4 J D. ?2.9 J E. ?15 J
In a ballistics test, a 28-g bullet pierces a sand bag that is 30cm thick
If the initial bullet velocity was 55m/s and it emerged from the sandbag moving at 18m/s what was the magnitude of the friction force (assuming it to be constant) that the bullet experienced while it traveled through the bag? A) 1.3 N B) 130 N C) 38 N D) 13 N
Power: A 5.0-V battery storing 43.0 kJ of energy supplies 1.5 A of current to a circuit. How much energy does the battery have left after powering the circuit for 1.0 h?
A. 16 kJ B. 27 kJ C. 43 kJ D. 41 kJ
In the simplified Drake equation, the total number of life-bearing planets in our galaxy is given by
A) NHP B) flife C) NHP × flife D) NHP / flife