Forces of 8 N and 3 N act on an object. If the two forces act in opposite directions, the net force on the object is
A) 8 N.
B) zero.
C) 11 N.
D) 5 N.
E) impossible to determine.
D
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A miniature heat sink heat exchanger is constructed with circular cross section channels (similar to that in Example 7.4), each of which has a diameter of 3.0 mm, drilled through a rectangular block. Cooling water at 20°C flows at the rate of 0.5 kg/h through each circular pipe, which has a constant surface temperature of 80°C. Assuming fully developed velocity and temperature distribution conditions, determine the length of the drilled pipe if the outlet water temperature is 60°C. Also, based on your calculations, verify the fully developed condition assumption.
GIVEN • Heat exchanger constructed with circular cross section channels. • Diameter of channel (Di)= 3 mm = 3*10-3 m • Cooling water inlet temperature (Tin)= 200C • Cooling water flow rate (m• )=0.5 kg/h = 1.39*10-4 kg/s • Cooling water outlet temperature (Tout)= 600C • Surface temperature(Ts)=800C FIND (a) Length of the drilled pipe. (b) Verify fully developed condition assumption PROPERTIES AND CONSTANTS or Water at 60°C: Density (?) = 982.8 kg/m3 Specific heat (cp) = 4182.8 J/(kg K) Thermal conductivity (k) = 0.657 W/(m K) Absolute viscosity (?) = 483.7 × 10–6 (Ns)/m2 Prandtl Number (Pr) = 3.02
A 4.00 kg ball is moving at 4.00 m/s to the EAST and a 6.00 kg ball is moving at 3.00 m/s to the NORTH. The total momentum of the system is
A. 14.2 kg m/s at an angle of 48.4 degrees SOUTH of EAST. B. 48.2 kg m/s at an angle of 24.2 degrees SOUTH of EAST. C. 48.2 kg m/s at an angle of 48.4 degrees NORTH of EAST. D. 24.1 kg m/s at an angle of 24.2 degrees SOUTH of EAST. E. 24.1 kg m/s at an angles of 48.4 degrees NORTH of EAST.
In Ptolemy's view of the universe, a planet moves on an epicycle whose center moves around the Earth on the deferent circle
a. Correct
b. FALSE; Ptolemy put the Sun at the center.
c. FALSE; The planet stays on the deferent circle.
d. FALSE; The Earth is at the center of the epicycle.
e. FALSE; Both c and d are correct.
The motions of a car and a truck along a straight road are represented by the velocity-time graphs in the figure. The two vehicles are initially alongside each other at time t = 0. At time T, what is true about these two vehicles since time t = 0?
A) The truck will have traveled further than the car. B) The car will have traveled further than the truck. C) The truck and the car will have traveled the same distance. D) The car will be traveling faster than the truck.