Kinetic energy is a scalar, equal to one-half an object's mass times the square of its speed. Like potential energy and work, kinetic energy does not have a direction associated with it.

The net force on the block is F - Ff = F - μkFN = F -μkFw = (18 N) - (0.4)(20 N) = 10 N. Since Fnet = ma = ()a, we find that 10 N = []a, which gives a = 5 m/s2.

The correct answer is (A). The longest leg the dog walked is the eastward vector. The fact that some of the length of the vector was later cancelled when the dog walked in the opposite direction does not change the length of the individual vector.

The gravitational force points downward while the book's displacement is upward. Therefore, the work done by gravity is -mgh = -(2 kg)(10 N/kg)(1.5 m) = -30 J.

The correct answer is (E). This is Einstein's statement concerning the relationship between the natural laws of physics and frames of reference. All physical laws are the same for systems that are moving at constant rate.

The correct answer is (E). Look at the graph of velocity. It is a straight line. The velocity increases by the same amount each second, additional proof that V = at.

The correct answer is (D). Power is the rate at which work is done, Power = work/time. The weight lifter lifted the weights up from the floor to a distance of 2.25 m above the floor in a time of .65 seconds. The work the weight lifter did to raise the weights can be calculated either by (F·s·cosθ) or by using the potential energy (mgh). Divide the work by the time he took to raise the weights, and the power he develops is 6923 watts.

The correct answer is (E). A chain reaction (industrial fission is a chain reaction) continues because of the neutrons that are emitted in the fissioning of each U-235 atom.

The correct answer is (E). The atoms and molecules of a solid are packed together more tightly than they are in a liquid. Liquid particles are able to slide over one another, but they are still in contact. Gaseous atoms and molecules have gained enough energy to move away from one another.

The correct answer is (D). Current is induced into a wire when the wire is placed in a changing magnetic field because of the moving line of flux crossing the wire. This is one of the ways a current is magnetically induced into a wire.

From the equation λf = c, we find that

The correct answer is (A). Light rays leaving an optically more dense material and striking the surface interface between the two substances are totally reflected back into the material when the angle of incidence is equal to or less than the critical angle.

The correct answer is (C). The first law of thermodynamics is the answer here. (delta)Q = (delta)U + (delta)W. The work done by the system is 70 Joules, but 150 Joules of heat was added. Rearrange the first law equation and subtract the work from the input heat to find the increase in internal energy. (delta)Q - (delta)W = (delta)U leads us to 150J - 70J = 80J.

The correct answer is (C). The listener hears the sound waves being bunched together as the siren approaches him, causing the pitch of the sound he hears to increase. When the fire truck passes the listener, the sound waves seem to be spread apart as the pitch of the sound decreases due to the lengthening of the sound waves.

The correct answer is (E). When the light is incident to the surface of the second material, a small amount of reflection occurs even though most of the light passes through the surface interface and into the second substance. This means the law of reflection is in effect for the reflected part of the light ray, the angle of reflection equals the angle of incidence.

By definition, electric field vectors point away from a positive source charge and toward a negative source charge. Furthermore, since an electron (which is negatively charged) would be repelled from a negative source charge, the resulting electric force on an electron would point away from a negative source charge, in the opposite direction from the electric field vector.

The correct answer is (B). One of two postulates of Einstein's theory of special relativity is that the speed of light in a vacuum is the same for all observers.

In order to balance the mass number (the superscripts), we must have 2 + 63 = 64 + A, so A = 1. In order to balance the charge (the subscripts), we need 1 + 29 = 30 + Z, so Z = 0. A particle with a mass number of 1 and no charge is a neutron, .

When a projectile moving in a parabolic path reaches the top of its path, its vertical velocity is instantaneously zero. A is a trap; it is wrong because the projectile has a (constant) horizontal velocity during its entire flight. B and D are equivalent, so both can be eliminated. C can also be eliminated; the weight of the projectile points downward, and when the projectile is at the top of its path and has a purely horizontal velocity, the force of air resistance is also horizontal. There is no reason why the vertical force must have the same magnitude as the horizontal force. The answer must be E.

Use the equation P = .

The second postulate of Einstein's theory of special relativity states that the speed of light is a universal constant (c = 3e8 m/s), regardless of the motion of the source or the detector. So despite the fact that the spaceship is approaching the planet at a speed of c/2, occupants of the ship will still measure the speed of light to be c. The time it takes the light pulse to travel a distance of 4.5e8 m is

The correct answer is (A). The definition of the frequency of a wave system is the number of waves per unit time, which is the same as saying the number of crests that pass a given point over a given time.

The correct answer is (E). The goldfish is pushed along by the water as a part of the action-reaction force pair as stated in Newton's Third Law.

The correct answer is (B). The kite rotates around a 5 m circumference in 1 second (C = 2 πr). Although the path of the kite is circular, it travels 5 m every second. The velocity is v =5m/1s=5m/s.

The correct answer is (C). The momentum of the pitched ball is changed by the impulse Ft. The catcher reduces the magnitude of the force on his hand by increasing the time required to change the momentum of the ball.

Use the work-energy theorem. 4 resistors in series = 24ohm 3 resistors in parallel together with one resistor in series with the parallel resistors = 8ohm 2 resistors in parallel together that are in series with 2 more resistors that are in parallel together = 6ohm

The correct answer is (B). Half-life means that half of the substance decays away during that time. Over 48 hours there are 6 half-lives.

The correct answer is (B). A voltage of 24 V should yield a current of 6A when it is hooked to a 4ohm resistor. The internal resistance of the battery is found . The extra .8ohm of resistance is the internal resistance of the battery.

The correct answer is (E). Work is defined as a force applied through a distance. The weight lifter did not move the weights through any distance after he lifted them overhead. He just stood holding the weights overhead, which does not meet the meaning of work in a physics sense.

The correct answer is (B). The resistance is calculated by using the power equation, R = V2/P. The solutions are:

The correct answer is (B). One of the basic postulates in Einstein's Theory of Relativity is the speed of light, which is constant for everyone.

The impulse delivered to the ball, J = F∆t, equals its change in momentum. Since the ball started from rest, we have

The correct answer is (D). An electric current is passed through an electromagnet or rotor, which causes it to spin within an applied magnetic field. The spinning rotor is the source of mechanical energy that is derived from electrical energy.

The correct answer is (D). The centripetal force required to keep a satellite in orbit remains constant. That means the closer to earth a satellite is, the faster it must travel in its orbit Fc = mV2/r . The farther the satellite is located from the earth, the slower it travels in orbit.

Since the centripetal force on each satellite is equal to the gravitational force it feels due to the earth, the question is equivalent to, How does FA, the gravitational force on satellite A, compare to FB, the gravitational force on satellite B?  Because both satellites have the same mass, Newton's law of gravitation tells us that the gravitational force is inversely proportional to r2. Since satellite B is 3 times farther from the center of the earth than satellite A, the gravitational force that satellite B feels is the gravitational force felt by satellite A. (Be careful if you tried to apply the formula Fc = for centripetal force and concluded that the answer was B. This is wrong because even though both satellites orbit at a constant speed, they don't orbit at the same speed, so the formula for centripetal force cannot be used directly.)

The correct answer is (E). The phase change to melt the ice drains all the heat from the water. At 0 degrees celsius ice will no longer melt because all the heat has been removed from the water.

The impulse delivered to the ball is equal to its change in momentum. The momentum of the ball was mv before hitting the wall and m(-v) after. Therefore, the change in momentum is m(-v) - mv = -2mv, so the magnitude of the momentum change (and the impulse) is 2mv.

The correct answer is (E). The higher the frequency of a photon, the more energy it has, therefore the more energy it can impart to the electron.

Let m be the mass of a satellite orbiting the earth in a circular orbit of radius r at a constant speed of v. Since the centripetal force is provided by the gravitational force due to the earth (mass M), we can write . Solving for v gives us v = . This result tells us that the mass of the satellite is irrelevant; only the mass of the earth, M, remains in the formula. Since v is inversely proportional to the square root of r, the satellite that's closer will have the greater speed. In this case, since Satellite #1 has the smaller orbit radius, it has the greater speed, and, since the radius of its orbit is

Eliminate A because Newton's Law of Universal Gravitation is reason to believe that Newton worked on gravitation. Eliminate B because Einstein may be best known for relativity, so he did work on relativity. Eliminate C because the unit of capacitance is named after Faraday, so Faraday must have worked on electricity and magnetism. For D, though, Coulomb's Law and the unit of electric charge are both named after Coulomb, which suggests that he significantly predated quantum mechanics and worked on the fundamentals of classical electrostatics; in fact, he was most active in the late 1700s, well before the quantum mechanics of the 1920s. Eliminate E because the Bohr model of an atom is definitely a product of Bohr's work on atomic structure.