A mass of 100 g is attached to one end of a massless rod, 10 cm in length, which is pivoted about the opposite end. The rod is held vertical, with the mass at the top, and released. The rod swings
What is the speed of the mass at the instant that the rod is horizontal? A)
0.71 m/s
B)
4.0 m/s
C)
2.0 m/s
D)
1.4 m/s
E)
2.8 m/s
D
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In a series LRC circuit an inductor will be dominant at higher frequencies
Indicate whether the statement is true or false
As a body falls through air starting from rest, its velocity
a. stays constant b. continuously decreases c. continuously increases d. gets larger and larger, eventually reaching a constant value e. gets smaller and smaller, eventually approaching zero
An object with an initial velocity of 3.50 m/s moves east along a straight and level path. The object then undergoes a constant acceleration of 1.80 m/s2 east for a period of 5.00 s. How far does the object move while it is accelerating?
(F) 6.30 m (G) 17.5 m (H) 27.2 m (J) 40.0 m
A thermocouple is made up of a spherical bead bimetallic junction at the end of two very thin wires of different materials. For example, in a type-T thermocouple, a copper wire and a constantan wire, with wire diameters ranging from 0.5 mm to 0.025 mm, are fused together to make a spherical bead that is also of a similar order-of-magnitude diameter. For such a thermocouple, determine the appropriate diameter of the spherical bead junction so as to ensure a response time of less than 2 s (?t ? 2 s) in water, which is at 40°C and has a convective heat transfer coefficient of 80 h = W/m2 K. Consider the bead junction to have properties of Cu, and to be initially at 150°C. Also, for the calculated bead diameter, what would be the response time in air at 40°C and 10 h = W/m2 K?
GIVEN • Copper and constanton wire with diameter range from 0.5 mm to 0.025 mm fused together • Response time ?t ? 2 s • Water bath temperature (T?) = 40°C • Convective heat transfer coefficient ( ch ) = 80 W/(m2 K) • Initial temperature of bead junction (T0)=1500 FIND • Appropriate diameter of spherical bead junction to ensure response time of less than 2 seconds. • Response time in air at 40°C and 10 h = W/m2 K for calculated bead diameter. ASSUMPTIONS • Constant thermal conductivity • End effects are negligible PROPERTIES AND CONSTANTS we get for Copper ks =391 W/m K c = 383 J/kg K ?=8930 kg/m3