FINAL REVIEW SHORT ANSWER Ch. 9
1.Energy is the ability to do work. Work is a transfer of energy.
2.Kinetic energy is the energy of motion, and potential energy is an object's energy due to its position or shape.
3.An object's thermal energy depends on its temperature, the arrangement of its particles, and the number of particles in the object.
4.Sample answer: When a substance forms, work is done to bond particles of matter together. The energy that creates the new bonds is stored in the substance as potential energy.
5.An energy conversion is a change from one form of energy into another. Any form of energy can be converted into any other form of energy.
6.Sample answer: In an iron, electrical energy is converted into thermal energy.
7.Answers will vary, but students should include that potential energy is converted into kinetic energy, kinetic energy into potential, and both potential and kinetic into thermal energy because of friction. All energy is conserved because some energy becomes thermal energy.
8.In every system, some of the energy put in is converted into thermal energy that is waste energy. A machine cannot run forever unless energy is continually added.
9.Answers will vary but should include the fact that both result from living things and both can be burned to release energy. Fossil fuels are millions of years old, while biomass is organic matter obtained from living things today.
10.Nuclear energy is a nonrenewable resource because the elements from which it is generated are in limited supply.
11.Sample answer: The steam turning the turbine that generated electrical energy comes from water heated by the burning of a fossil fuel, such as coal. The coal is a result of organisms that lived millions of years ago that used light energy from the sun.
12.Renewable resources include solar energy, energy from water, wind energy, geothermal energy, and biomass.
13.Sample answer: Without the sun as the source of most energy, we would eventually run out of energy resources.
14.The pendulum has maximum potential energy at points A and E.
15.The pendulum has maximum kinetic energy at point C.
FINAL REVIEW SHORT ANSWER Ch. 8
1.The pitcher is no longer doing work on the ball as it flies through the air because he is no longer exerting a force on it. (However, work is being done on the ball by the Earth, which exerts a force on the ball and pulls it back toward the ground.)
2.Work occurs when a force causes an object to move in the direction of the force, and power is the rate at which work is done. The more work you do in a given amount of time, or the less time it takes you to do a given amount of work, the greater your power.
3.Work is done on the chair only when it is picked up, not when it is carried across the room. Therefore, W = 50 N 0.5 m = 25 J.
4.Sample answer: Using a ramp makes work easier because it allows you to apply a smaller input force than you would have to apply when lifting a load straight up. However, the smaller force has to be exerted over a longer distance.
5.Sample answer: A machine can't be 100 percent efficient because some of the work input is used to overcome friction. Therefore, work input is always greater than work output.
6.MA = 300 N 15 N = 20
7.Examples include the crank on a can opener, the reel on a fishing rod, a screwdriver, a doorknob, the crank on an ice cream maker, and the film-advance mechanism on an old camera.
8.Each side of the tweezers is a third-class lever. The sharpened edges of nail clippers are wedges, and the arm that activates the clipper is a second-class lever.
9.A force must be exerted on an object, and the object must move in the direction of the force.
10.A total of 225 J of work has been done.
11.This motor has 180 W of power.
12.A machine makes work easier by changing the size or direction, or both, of a force.
13.Work input and work output must be known in order to calculate mechanical efficiency.
14.
a.Work = 1,000 N 10 m = 10,000 J
b.Power = 10,000 J 100 s = 100 W
FINAL REVIEW SHORT ANSWER Ch. 7
1.The moving particles in a fluid collide against each other and against the walls of the container. This creates pressure.
2.The pressure exerted by the fluids in your body works against atmospheric pressure.
3.Water pressure increases with depth. Therefore, more pressure is exerted at the bottom of the dam than at the top. The dam must be thicker at the bottom to withstand this added pressure.
4.Pascal's principle states that a change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of that fluid.
5.The pressure inside the balloon is increased equally at all points because changes in fluid pressure are transmitted equally to all parts of an enclosed fluid.
6.a.15 N
b.It will sink because its weight is greater than the buoyant force acting on it.
7.It will float because it is less dense than mercury.
8.Whether an object sinks or floats depends on density, not weight. A heavy object can have an overall density that is less than that of water and can therefore float.
9.Fluid pressure decreases.
10.Drag is the force that opposes motion through a fluid.
11.As the fluid speed between the boats increases, the fluid pressure decreases. The pressure on the outer sides of the boats then becomes greater than the pressure between them. This increased pressure from the outside can push the boats together, causing them to collide.
12.They are both fluids.
13.As depth increases, the weight of the fluid above increases, which increases pressure.
14.Determine the weight of the volume of fluid displaced by the object.
15.Lift, thrust, drag, and gravity are forces that act on an aircraft.
16.Shower curtains often have weights or magnets at the bottom in order to prevent them from being pushed toward the water stream.
17.Liquids are used in hydraulic brakes because liquids cannot be compressed easily. Gases are compressible.
FINAL REVIEW SHORT ANSWER Ch. 6
1.Air resistance slows or stops the acceleration of falling objects.
2.An orbit is formed by combining two motions: a forward motion and free fall toward Earth. The path that results is a curve that matches the curve of Earth's surface.
3.Newton's first law says that matter resists any change in motion. Inertia is the tendency of objects (matter) to resist changes in motion. Newton's first law is also known as the law of inertia.
4.You can increase the acceleration of an object by increasing the force causing the acceleration or by reducing the object's mass.
5.If the acceleration due to gravity were doubled, your weight would double. This is because of Newton's second law: F = ma. Weight is the force due to the acceleration on mass. If acceleration is doubled and mass remains the same, the force (weight) is doubled, too.
6.The elephant—it has both a greater mass and greater velocity.
7.A ball rolling across the table has only horizontal motion. Once the ball rolls off the edge, gravity pulls it downward, giving it both vertical and horizontal motion, which causes a curved path.
8.On the moon, both will hit the ground at the same time because there is no atmosphere and no air resistance. On Earth, the hammer will hit the ground first because the feather will be slowed much more by air resistance.
9.The bicycle has a smaller mass, so a smaller force is required to give it the same acceleration as the car.
10.You can increase the force applied to the cart, or you can decrease the mass of the cart by removing some of the objects from it.
11.The hot gases expelled from the back of the rocket produce a reaction force on the rocket that lifts and accelerates the rocket.
12.An Earth orbit is formed by combining the forward motion of the orbiting object with free fall toward Earth. The path that results is a curve that follows the curve of the Earth.
13.You will move away from your friend (in the direction opposite from where you throw the backpack). The action force is you pushing the backpack toward your friend. The reaction force is the backpack pushing you away from your friend.
14.a.v = gt = 9.8 m/s/s 1.5 s = 14.7 m/s
b.F = m a = 12 kg 9.8 m/s/s = 117.6 N
15.v = g t = 9.8 m/s/s 3.5 s = 34.3 m/s
At the time of impact, the stone was traveling at a velocity of 34.3 m/s.
FINAL REVIEW SHORT ANSWER Ch. 5
1.You must know the distance traveled and the time taken to travel that distance.
2.Speed does not include direction; velocity does.
3.Acceleration is the rate at which velocity changes.
4.Yes, a change in direction does affect acceleration. Acceleration is a measure of velocity change. Velocity is speed in a given direction, and a velocity changes if direction changes.
5.Unbalanced forces occur when the net force on an object is not zero and cause a change in an object's motion. Balanced forces occur when the net force equals zero and do not cause a change in an object's motion.
6.Friction occurs because the microscopic hills and valleys of two touching surfaces "stick" to each other.
7.Answers will vary; accept all reasonable answers. Sample answers: Sliding friction is used while skiing and writing with a pencil. Rolling friction is used while riding a bicycle and pushing a handcart. Fluid friction is used while swimming and throwing a softball.
8.The greater an object's mass, the larger the gravitational force it exerts on other objects.
9.As the distance between objects increases, the gravitational force between them decreases; as the distance between objects decreases, the gravitational force between them increases.
10.A person's weight decreases in orbit because the distance between the person and the Earth would increase. But the person's mass would remain constant, because mass is the amount of matter in an object, and it does not depend on gravitational force.
11.Centripetal acceleration is acceleration that occurs in circular motion.
12.To calculate speed, divide the distance traveled by the time.
13.To calculate velocity, divide the distance and direction traveled by the time.
14.To calculate acceleration, subtract the starting velocity from the final velocity, and divide it by the time it takes to change velocity.
15.A net force is the sum of all the forces acting on an object.
16.Gravity is a force of attraction between objects that is due to the masses of the objects.
17.8 N north
FINAL REVIEW SHORT ANSWER Chapter 20
1.The particles in a longitudinal wave vibrate back and forth along the direction the wave is traveling. The particles of a transverse wave vibrate perpendicularly to the direction the wave is traveling.
2.Frequency is the number of waves that pass by in a given amount of time. Wave speed is the distance a wave travels in a given amount of time.
3.Waves bounce off barriers during reflection. Waves bend when entering a new medium at an angle during refraction.
4.Wavelength is the distance between any two adjacent crests (or compressions) in a series of waves. Amplitude is the maximum distance particles travel from their rest position.
5.As a transverse wave moves through a medium, the particles vibrate at right angles to the direction of the wave. In longitudinal waves, the particles vibrate back and forth along the wave's path.
6.Waves transfer energy but not matter. The leaf would just bob up and down; it would not move with the wave toward the shore.
7.Sound waves are mechanical waves and therefore cannot travel through space. However, visible light is an electromagnetic wave and therefore can travel through space.
8.v = f = 2 m 6 Hz = 12 m/s
9.The amplitude of the speedboat waves was larger than that of the breeze waves. The frequency of the speedboat waves was lower than that of the breeze waves. However, the speedboat waves had more effect on the boat, so they most likely had more energy.
10.Reflection and diffraction can occur when a wave encounters a barrier.
11.
12.When two waves with the same amplitude overlap so that the crests of one wave overlap the troughs of the other, they cancel each other out through destructive interference. This results in a “flat” wave.
13.rank: b, c, a Wave b has a high frequency and a large amplitude. Wave c has a high frequency and a small amplitude. Wave a has a low frequency and a small amplitude. High frequency and large amplitude = more energy, low frequency and small amplitude = less energy
14.Yes; because waves are not matter, they do not have volume. So more than one wave can exist in the same place at the same time, resulting in interference.