The temperature is observed to decrease from
to 
during the evening of a very hot day. What is the relative change in the speed of sound over this time interval?
A. -15%
B. -28%
C. -1.5%
D. -3%
C. -1.5%
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A 70.0-kg man jumps 1.00 m down onto a concrete walkway. His downward motion stops in 0.04 seconds. If he forgets to bend his knees, what force is transmitted to his leg bones?
a. 700 N c. 8000 N b. 4000 N d. 16,000 N
High-strength stainless steel is required for use in building structures and equipment (e.g. , cranes). It is produced by heat treating quench-hardened steel in a process called tempering that reduces brittleness and imparts toughness. In a production facility, alloy steel plates (k=50 W/(m K), c=460 J/(kg K) and ?=7865 kg/m3) of thickness 3 cm have to be tempered in a convective oven by heating them to 5500C. If the plates are initially at 400C and the air inside the heat treating oven is at 7000C with a convective heat transfer coefficient of 45 W/(m2 K), determine how long the plate has to remain in the oven.
GIVEN
• Alloy steel plate of thickness L=3 cm=0.03 m
• Tempering in oven to 5500C
• Initial temperature of the plate (To) = 40°C
• Heat treating oven temperature (T?) = 700°C
• Convective heat transfer coefficient ( ch ) = 45 W/(m2 K)
FIND
• The time required for the plate to reach 5500C.
ASSUMPTIONS
• Constant thermal conductivity
• End effects are negligible
SKETCH
Evidence that there is a considerable amount of water frozen under the surface of Mars is provided by all of the following except
A. satellite measurements of water in the polar caps. B. discovery by the Mars rovers of chemicals in surface rocks formed in the presence of large amounts of water. C. squishy-looking flow patterns around crater impact sites. D. features resembling channels cut by flowing water. E. periodic eruptions of geysers when subsurface ice is melted by volcanic activity.
An object is thrown upwards with a speed of 14 m/s. How high above the projection point does it reach?
A) 5.0 m B) 10 m C) 15 m D) 20 m E) 25 m