phys

23問 • 2年前

問題一覧

A solid cube of aluminum is 2.00 cm on each edge. The relative density of aluminum is 2.70. Find its mass.

21.6 g

(a) Calculate the absolute pressure at the bottom of a freshwater lake at a point whose depth is 27.5 m. Assume the density of the water is 1.00 x 103 kg/m3 and that the air above is at a pressure of 101.3 kPa. (b) What force is exerted by the water on the window of an underwater vehicle at this depth if the window is circular and has a diameter of 35.0 cm?

Water flowing through a garden hose of diameter 2.74 cm fills a 25-L bucket in 1.50 min. (a) What is the speed of the water leaving the end of the hose? (b) A nozzle is now attached to the end of the hose. If the nozzle diameter is one-third the diameter of the hose, what is the speed of the water leaving the nozzle?

On a day when the temperature reaches 50°F, what is the temperature in degrees Celsius and in kelvins? A pan of water is heated from 25°C to 80°C. What is the change in its temperature on the Kelvin scale and on the Fahrenheit scale?

Heating a 24.0-g aluminum can raises its temperature by 15.0°C. Find the value of Q for the can. Specific heat of aluminum is 0.900 J/g°C.

How much energy is required to change a 40.0-g ice cube from ice at -10.0°C to steam at 110°C?

A 0.0500-kg ingot of metal is heated to 200.0°C and then dropped into a beaker containing 0.400 kg of water initially at 20.0°C If the final equilibrium temperature of the mixed system is 22.4°C, find the specific heat of the metal.

What mass of steam initially at 130°C is needed to warm 200 g of water in a 100-g glass container from 20.0°C to 50.0°C?

A glass windowpane in a home is 0.620 cm thick and has dimensions of 1.00 m x 2.00 m. On a certain day, the temperature of the interior surface of the glass is 25.0°C and the exterior surface temperature is 0°C. (a) What is the rate at which energy is transferred by heat through the glass? (b) How much energy is transferred through the window in one day, assuming the temperatures on the surfaces remain constant?

A bar of gold is in thermal contact with a bar of silver of the same length and area. One end of the compound bar is maintained at 80.0°C while the opposite end is at 30.0°C. When the energy transfer reaches steady state, what is the temperature at the junction?

A student is trying to decide what to wear. The surroundings (his bedroom) are at 20.0°C. If the skin temperature of the unclothed student is 35°C, what is the net energy loss from his body in 10.0 min by radiation? Assume that the emissivity of skin is 0.900 and that the surface area of the student is 1.50 m².

The surface of the Sun has a temperature of about 5 800 K. The radius of the Sun is 6.96\times10^{8}m Calculate the total energy radiated by the Sun each second. Assume that the emissivity of the Sun is 0.965.

Consider three point charges located at the corners of a right triangle as shown, where q_{1}=q_{0}=5.0~\mu C q = -2.0 µC, and a = 0.10 m. Find the resultant force exerted on q.

Three point charges lie along the xaxis as shown. The positive charge a=15.0~uc is at m, the positive charge x=600 µC is at the origin, and the resultant force acting on q is zero. What is the x coordinate of q?

An electric heater is constructed by applying a potential difference of 120 V to a Nichrome wire that has a total resistance of 8.00 Ω. Find the current carried by the wire and the power rating of the heater.

(a) What is the required resistance of an immersion heater that will increase the temperature of 1.50 kg of water from 10.0°C to 50.0°C in 10.0 min while operating at 110 V? (b) Estimate the cost of heating the water if the energy is purchased at an estimated price of 10.0 ¢ per kilowatt-hour.

Consider the circuit shown in the figure. Find (a) the current in the 20.0-Q resistor and (b) the potential difference between points a and b.

Using Kirchhoff's rules, (a) find the current in each resistor in the figure shown. (b) Find the potential difference between points c and f. Which point is at the higher potential?

An electron in a television picture tube moves toward the front of the tube with a speed of 8.0 × 10 m/s along the x axis. Surrounding the neck of the tube are coils of wire that create a magnetic field of magnitude 0.025 T, directed at an angle of 60° to the x axis and lying in the xy plane. Calculate the magnetic force on the electron.

At the equator, near the surface of the Earth, the magnetic field is approximately 50.0 µT northward, and the electric field is about 100 N/C downward in fair weather. Find the gravitational, electric, and magnetic forces on an electron in this environment, assuming the electron has an instantaneous velocity of 6.00 × 10⁶ m/s directed to the east.

A wire 2.80 m in length carries a current of 5.00 A in a region where a uniform magnetic field has a magnitude 0.390 T. Calculate the magnitude of the magnetic force on the wire assuming the angle between the magnetic field and the current is (a) 60.0°, (b) 90.0°, (c) 120°.

A 50.0-turn circular coil of radius 5.00 cm can be oriented in any direction in a uniform magnetic field having a magnitude of 0.500 Τ. If the coil carries a current of 25.0 mA, find the magnitude of the maximum possible torque exerted on the coil.

A rectangular coil consists of N=100 closely wrapped turns and has dimensions a=0.400 m and b=0.300~m The coil is hinged along the y axis, and its plane makes an angle ø = 30.0° with the xaxis (Fig. P29.51). (a) What is the magnitude of the torque exerted on the coil by a uniform magnetic field B=0.800 T directed in the positive x direction when the current is I=1.20 Ain the direction shown? (b) What is the expected direction of rotation of the coil?

Pg 1. Radio-and-Television

Jian Estelle · 23問 · 2年前

Pg 1. Radio-and-Television