If an electron is accelerated from rest through a potential difference of 300 V, find its approximate speed at the end of this process. (e = 1.6 10-19 C; me = 9.1 10-31 kg)
a. 2.5 107 m/s
c. 1.0 107 m/s
b. 2.1 107 m/s
d. 1.4 107 m/s
[Ques. 2] A 90-kg halfback running north with a speed of 10 m/s is tackled by a 120-kg opponent running south at 5.0 m/s. The collision is perfectly inelastic. Compute the velocity of the two players just after the tackle.
a. 1.4 m/s south
c. 2.8 m/s north
b. 2.8 m/s south
d. 1.4 m/s north
[Ques. 3] A proton (+1.6 10-19 C) moves 10 cm along the direction of an electric field of strength 4.0 N/C. The electrical potential difference between the proton's initial and ending points is:
a. 4.8 10-19 V.
c. 0.044 V.
b. 0.40 V.
d. 6.4 10-19 V.
[Ques. 4] In an inelastic collision between two objects with unequal masses:
a. the velocity of one will increase by the amount that the velocity of the other decreases.
b. the momentum of one will increase by the amount that the momentum of the other decreases.
c. the energy of one increases by the amount that the energy of the other decreases.
d. the total momentum of the system will decrease.
[Ques. 5] Two equal positive charges are separated by d. Then one of the charges is replaced by a negative charge of the same magnitude. Take the potential at infinity to be zero. In which situation is the potential higher midway between the charges; is this value of potential zero?
a. the first situation; no
c. the second situation; no
b. the first situation; yes
d. the second situation; yes
[Ques. 6] A miniature, spring-loaded, radio-controlled gun is mounted on an air puck. The gun's bullet has a mass of 5.00 g, and the gun and puck have a combined mass of 130 g. With the system initially at rest, the radio-controlled trigger releases the bullet, causing the puck and empty gun to move with a speed of 0.500 m/s. Of the total kinetic energy of the gun-puck-bullet system, what percentage is in the bullet?
a. 50
c. 3.4
b. 96
d. 100
[Ques. 7] Two charges, each of charge q, are separated by a distance d. The distance between the charges is doubled. If the original potential energy of the arrangement was 40 mJ, by how much does the potential energy change when the charges are moved to the increased distance?
a. It decreases by more than 20 mJ.
c. More information is needed. b. It decreases by less than 20 mJ
d. It decreases by 20 mJ.
[Ques. 8] A railroad freight car, mass 15,000 kg, is allowed to coast along a level track at a speed of 2.0 m/s. It collides and couples with a 60,000-kg loaded second car, initially at rest and with brakes released. What percentage of the initial kinetic energy of the 15,000-kg car is preserved in the two-coupled cars after collision?
a. 20
c. 86
b. 23
d. 100
[Ques. 9] Two protons, each of charge 1.60 10-19 C, are 3.00 10-5 m apart. What is the change in potential energy if they are brought 1.00 10-5 m closer together? (ke = 8.99 109 Nm2/C2)
a. 3.84 10-24 J
c. 1.15 10-23 J
b. 3.20 10-16 J
d. 3.20 10-19 J
[Ques. 10] A 20-g bullet moving at 1000 m/s is fired through a one-kg block of wood emerging at a speed of 200 m/s. What is the change in the kinetic energy of the bullet-block system as a result of the collision assuming the block is free to move?
a. 0 J
c. 9.5 kJ
b. -9.5 kJ
d. -18 J
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