The figure shows two 1.0 kg-blocks connected by a rope. A second rope hangs beneath the lower block. Both ropes have a mass of 250 g. The entire assembly is accelerated upward at 2.3 m/s2 by force . What is the tension at the top end of rope 1?
A) 18 N
B) 15 N
C) 2.9 N
D) 3.5 N
Answer: A
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This graph plots planetary mass on the horizontal axis and planetary radius on the vertical axis. Which of the four points marked by one of the bold numbers 1 through 4 represents a planet that has about the same composition as Earth but is larger in both size and mass?
A) Point 1 B) Point 2 C) Point 3 D) Point 4
A high-speed computer is located in a temperature controlled room of 26°C. When the machine is operating its internal heat generation rate is estimated to be 800 W. The external surface temperature is to be maintained below 85°C. The heat transfer coefficient for the surface of the computer is estimated to be 10 W/(m2 K). What surface area would be necessary to assure safe operation of this machine? Comment on ways to reduce this area.
GIVEN
• A high-speed computer in a temperature controlled room
• Temperature of the room (T?) = 26°C
• Maximum surface temperature of the computer (Tc) = 85°C
• Heat transfer coefficient (U) = 10 W/(m K)
• Internal heat generation q
G= 800 W
FIND
• The surface area (A) required and comment on ways to reduce this area
ASSUMPTIONS
• The system is in steady state
SKETCH
This design involves only one optical surface, a concave mirror
A) prime focus reflector B) Newtonian reflector C) Cassegrain reflector D) Gregorian reflector E) refractor
A steel wire, 86.0 m long at 21°C, has a coefficient of linear expansion of 11 × 10^?6/C°. Give its change in length as the temperature changes from 21°C to 36°C
a. 2.0 cm b. 3.4 cm c. 1.4 cm d. 0.21 cm e. 6.3 cm