Calculating Power

(See Math Skills, page 415.)

1. While lifting a box 0.75 m straight up, you exert an upward force of 320 N on the box. How much work do you do on the box? What is the power if you take 2.0 s to lift the box?

2. A dog sled is pulled at a constant horizontal speed of 8.0 m/s by a team of dogs. What is the power of the dogs if they are applying a constant horizontal force of 200.0 N to the sled? (Hint: Calculate the work done in one second).

3. How much work can a 500-watt engine do in 1.0 hour?

Calculating IMA and AMA

(See Math Skills, page 425.)

1. A crowbar is 0.75 m long and the fulcrum is located 10.0 cm from the end of the bar. What is the ideal mechanical advantage of the crowbar?

2. A person changing a tire exerts a force of 520 N on a car jack to apply a lifting force of 12,000 N. What is the actual mechanical advantage of the car jack?

3. A pair of pliers has an actual mechanical advantage of 3.5. If you were to squeeze the handles together with a force of 3.0 N, how much force would the jaws of the pliers exert?

4. If a machine has an efficiency of 35%, and you do 1500 J of work on the machine, what will be the work output of the machine?

Kinetic Energy

(See Math Skills, page 448.)

1. A 13,000-kg automobile moves at 28 m/s. What is the automobile's kinetic energy?

2. Two birds fly at the same speed, 4.0 m/s. One bird has a mass of 0.25 kg and the other has a mass of 0.75 kg. What is the kinetic energy of each bird?

Conservation of Energy

(See Math Skills, page 458.)

1. An 80.0-kg diver climbs a ladder up to a high-dive platform 10.0 meters above the ground.

   1. How much gravitational potential energy does the diver gain?

   2. After diving, what is the diver's speed at the water? Assume all of the potential energy has been converted to kinetic energy.

2. A 4.0-kg bowling ball returns to a bowler along a horizontal track at a speed of 5.0 m/s. At the end of the track, the ball must rise up an incline to a height of 1.0 m. Show that the ball has enough energy to make it to the top of the ramp. Assume friction can be ignored.

Specific Heat

(See Math Skills, page 477.)

1. How much heat is needed to raise the temperature of a plastic beaker by 10.0°C? The beaker's mass is 24.4 g and the specific heat of the plastic is 1.90 J/g∙°C.

2. Tin has a specific heat of 0.23 J/g∙°C. How much heat is needed to raise the temperature of 550 g of tin from 65°C to 125°C?

3. What mass of water will change its temperature by 10.0°C when 500.0 J of heat is added to it?

Speed of Mechanical Waves

(See Math Skills, page 506.)

1. A wave on a rope has a wave-length of 1.5 m and a frequency of 3.0 Hz. What is the speed of the wave?

2. A motorboat in a lake makes a surface wave with a frequency of 13 Hz and a wavelength of 0.15 m. What is the speed of the wave?

3. Seven ocean wave crests pass by a pier in 28.0 s. If the wave speed is 11 m/s, what is the wavelength of the waves?

Calculating Wave Speed

(See Math Skills, page 535.)

1. A cell phone transmits a carrier wave at a frequency 1900 MHz. What is the wavelength of the wave? (Assume the wave moves at the speed of light in a vacuum.)

2. A carrier wave from an FM station has a frequency 94.5 MHz. What is the wavelength?

3. A light-emitting diode (LED) emits light with a wavelength of 630 nanometers. What is the frequency of the light and what color is the LED?

Power, Voltage, and Current

(See Math Skills, page 611.)

1. A flashlight uses a 6.0-W light bulb connected to 3.6-V nickel-cadmium battery. How much current does the bulb use?

2. A hair dryer has a power rating of 1600 W. If it is connected to a 120-volt line, how much current does it draw?

Table of Contents