A solid rock, suspended in air by a spring scale, has a measured mass of 8.50 kg. When the rock is submerged in water, the scale reads 4.00 kg. What is the density of the rock? (water density = 1 000 kg/m3)
a. 6.8E+2 kg/m3
b. 8.9E+2 kg/m3
c. 3.2E+2 kg/m3
d. 1.9E+3 kg/m3
e. 1.9E+6 kg/m3
d
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A baseball pitcher throws a fastball at 98 mph. He also has a slower "changeup" pitch, 75 mph, which he throws identically, same windup and same release angle from shoulder height. Which pitch gets to home plate with a flatter trajectory-i.e., velocity vector closer to horizontal?
A. The fastball B. The changeup C. They each have same trajectory, since the distance to home plate is the same
Four 12
resistors are connected together. What is the least resistance that can be attained with these resistors?
A. 12 
B. 6.0
C. 3.0
D. 2.0
E. 1.0
A 1500 W portable heater is needed to replace the heat lost through a circular window (radius 25 cm) in the wall of a home that is made of a single pane of glass 0.30 cm thick. Thermal conductivity for the glass is 0.63 W/mK. The temperature inside the house is 
and outside is 
What is the thickness of the window?
A. 0.84 mm B. 4.2 mm C. 2.6 mm D. 0.66 mm
A sealed container holds 0.020 moles of ideal nitrogen (N2 ) gas, at a pressure of 1.5 atm and a temperature of 290 K. The atomic mass of nitrogen is 14.0 g/mol
How many molecules of nitrogen are in the container? (R = 8.31 J/mol ? K, 1 atm = 101 kPa) A) 1.5 × 1021 mol B) 3.0 × 1021 mol C) 6.0 × 1021 mol D) 1.2 × 1022 mol E) 2.4 × 1022 mol