Your weight is equal to mg when you are
A) firmly supported on a horizontal surface and in equilibrium.
B) in Earth's gravitational field.
C) anywhere except in Earth's orbit.
D) all of the above
Answer: A
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The energy used by a 100-watt light bulb in 1 hour is
a. 0.01 J. b. 360,000 J. c. 100 J. d. 6,000 J. e. none of the above.
A hill is 200 m long and makes an angle of 12° with the horizontal. As a 50-kg jogger runs up the hill, how much work does gravity do on the jogger?
a. 98,000 J c. 20,000 J b. -20,000 J d. zero
On a hot summer day, the temperature is 40.0°C and the pressure is 1.01 × 105 Pa
Let us model the air as all nitrogen of molecular mass 28.0 g/mol having molecules of diameter 0.500 nm that are moving at their root-mean-square speed. Avogadro's number is 6.02 × 1023 molecules/mol, the ideal gas constant is 8.31 J/mol ? K, and the Boltzmann constant is 1.38 × 10-23 J/K. Calculate reasonable estimates for (a) the root-mean-square speed of the nitrogen molecules. (b) the average distance a typical molecule travels between collisions. (c) the average time a molecule travels between collisions, assuming that the molecules are moving at their root-mean-square speeds. (d) the number of collisions an average molecule undergoes per second. What will be an ideal response?
Why do white dwarfs have high temperatures?
A. chemical reactions on their surfaces B. heat left over from their formation C. nuclear fusion in their cores D. frictional heating from motions inside the white dwarfs