# Homework Help for Physics (page 90)

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31.11 - A 0.180-H inductor is connected in series with a 90.0-12 resistor and an ac source. The voltage across the inductor is v. = -(12.0 V)sin((480 rad/s)t]. a) Derive an expression for the voltage Ur across the resistor. (b) What is up at t = 2.00 ms?
7 Nov 2017
2.36 A small rock is thrown vertically upward with a speed of 22.0 m/s from the edge of the roof of a 30.0-m-tall building. The rock doesn't hit the building on its way back down and lands on the street below. Ignore air resistance. (a) What is the speed of the rock just before it hits the street? (b) How much time elapses from when the rock is thrown until it hits the street?
6 Nov 2017
87. Calculate the number of atoms in each sample. a. 5.18 g P b . 2.26 g Hg c. 1.87 g Bid. 0.082 g Sr
6 Nov 2017
1.3. How many nanoseconds does it take light to travel 1.00 ft in vacuum? (This result is a useful quantity to remember.)
4 Nov 2017
9.9. A bicycle wheel has an initial angular velocity of 1.50 rad/s. (a) If its angular acceleration is constant and equal to 0.200 rad/s?, what is its angular velocity at t = 2.50 s? (b) Through what angle has the wheel turned between t = 0 and t = 2.50 s?
3 Nov 2017
1.53 • BIO Breathing Oxygen. The density of air under stan- dard laboratory conditions is 1.29 kg/m", and about 20% of that air consists of oxygen. Typically, people breathe about 1 L of air per breath. (a) How many grams of oxygen does a person breathe in a day? (b) If this air is stored uncompressed in a cubical tank, how long is each side of the tank?
1 Nov 2017
42. Calculate the pH of the solution that results from each mixture. a. 150.0 mL of 0.25 M HF with 225.0 mL of 0.30 M NaF b. 175.0 mL of 0.10 M C2H5NH2 with 275.0 mL of 0.20 M C2H5NH3C1
1 Nov 2017
88. Calculate the number of atoms in each sample. a. 14.955 g CT b. 39.733 g S c. 12.899 g Pt d . 97.552 g Sn
1 Nov 2017
5.17 . A light rope is attached to a block with mass 4.00 kg that rests on a frictionless, horizontal surface. The horizontal rope passes over a frictionless, massless pulley, and a block with mass m is suspended from the other end. When the blocks are released, the tension in the rope is 15.0 N. (a) Draw two free-body diagrams: one for each block. (b) What is the acceleration of either block? (c) Find m. (d) How does the tension compare to the weight of the hanging block?
31 Oct 2017
31.3. The voltage across the terminals of an ac power supply varies with time according to Eq. (31.1). The voltage amplitude is V = 45.0 V. What are (a) the root-mean-square potential differ- ence Vrms and (b) the average potential difference Vay between the two terminals of the power supply?
30 Oct 2017
42. Given the values of AHxn, ASxn, and T, determine ASunty and predict whether or not each reaction is spontaneous. (Assume that all reactants and products are in their standard states.) a. AHix = -95 kJ; ASix = -157J/K; T = 298 K b. AHix = -95 kJ; ASix = -157J/K; T = 855 K C. AHxn = +95 kJ; ASix = -157J/K; T = 298 K d. AHX = -95 kJ; ASXn = +157J/K; T = 398 K
30 Oct 2017
97. The ratio of oxygen to carbon by mass in carbon monoxide is 1.33:1.00. Find the formula of an oxide of carbon in which the ratio by mass of oxygen to carbon is 2.00:1.00.
30 Oct 2017
11.30. A vertical, solid steel post 25 cm in diameter and 2.50 m long is required to support a load of 8000 kg. You can ignore the weight of the post. What are (a) the stress in the post; (b) the strain in the post; and (c) the change in the post's length when the load is applied?