A string is wrapped tightly around a fixed pulley that has a moment of inertia of 0.0352 kg m2 and a radius of 12.5 cm. The string is pulled away from the pulley with a constant force of 5.00 N. As the string unwinds the pulley begins to rotate
What is the speed of the string after it has unwound 1.25 m? A) 2.09 m/s
B) 2.36 m/s
C) 1.18m/s
D) 3.18 m/s
E) 4.95 m/s
B
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Based on current evidence, when is/was liquid water abundant on the surface of Mars?
A) only before about 3 billion years ago B) only during the first 1 million years of Mars's existence C) Water comes and goes, with the most recent water flows occurring a few thousand years ago. D) only during the most recent 1 billion years of Mars's history
The acceleration of a body is given by the slope of a graph plotting
A. velocity versus distance travelled. B. time versus velocity. C. time versus distance travelled. D. distance travelled versus time. E. velocity versus time.
A wire of perimeter P and cross-sectional area A emerges from a die at a temperature T (above ambient temperature) and with a velocity U. Determine the temperature distribution along the wire in the steady state if the exposed length downstream from the die is quite long. State clearly and try to justify all assumptions.
GIVEN
• A wire emerging from a die at a temperature (T) above ambient
• Wire perimeter = P
• Cross-sectional area = A
• Wire emerges at a temperature T above ambient
• Wire velocity = U
FIND
• The temperature distribution along the wire in the steady state if the exposed length downstream from the die is quite long. State clearly and try to justify all assumptions
ASSUMPTIONS
• Ambient temperature is constant at T?
• Heat transfer coefficient between the wire and the air is uniform and constant at hc
• The material properties of the wire are constant
? Thermal conductivity = k
? Thermal diffusivity = ?
• Axial conduction only
• Wire temperature is uniform at a cross section (negligible internal thermal resistance)
SKETCH
When a light ray in air enters water at 15° from the normal, it
A) always bends toward the normal. B) always bends away from the normal. C) sometimes bends towards or away from the normal. D) does not bend.