Download Q1 What is the approximate height of this room, to the nearest meter

Q6.2.a: A ball whose mass is 2 kg
travels at a velocity of
< 0, –3, 4> m/s.
What is the kinetic energy of the
ball?
1) < 0, –6, 8 > J
2) < 0, –3, 4 > J
3) 2 J
4) 10 J
5) 25 J
Q6.2.aa: A ball whose mass is 2
kg travels at a velocity of
< 0, –3, 4> m/s.
What is the kinetic energy of the
ball?
1) 0 J
2) 2 J
3) 10 J
4) 25 J
5) < 0, 9, 16 > J
Q6.2.b: A ball whose mass is 2 1) 0 J
kg travels at a velocity of
2) 25 J
< 0, –3, 4> m/s.
3) 6e8 J
4) 9e16 J
What is the rest energy of the
5) 1.8e17 J
ball?
Q6.2.c:
Consider an electron (mass 9e-31
kg) moving with speed v = 0.9c.
What is its rest energy?
1) 7.3e-31 J
2) 8.1e-14 J
3) 1.05e-13 J
4) 1.86e-13 J
5) 2.7e8 m/s
Q6.2.d:
Consider an electron (mass 9e-31
kg) moving with speed v = 0.9c.
What is its total (particle) energy?
1) 7.3e-31 J
2) 8.1e-14 J
3) 1.05e-13 J
4) 1.86e-13 J
5) 2.7e8 m/s
Q6.2.e:
Consider an electron (mass 9e-31
kg) moving with speed v = 0.9c. Its
rest energy is 0.81e-13 J, and its
(total) particle energy is 1.86e-13 J.
What is its kinetic energy?
1) 7.3e-31 J
2) 3.28e-14 J
3) 8.1e-14 J
4) 1.05`e-13 J
5) 1.86e-13 J
Q6.3.a: On a space station, you
pushed a box that was initially
floating at rest at location < 0, 0, 10 >
m to location < 0, 0, 14 > m, applying
a force < 0, 0, 5 > N. How much work
did you do on the box?
1) W = 20 J
2) W = 50 J
3) W = 70 J
4) W = 140 J
5) Not enough
information
Q6.3.b: You did 20 J of work on the box. What happened?
1) The box slowed down.
2) The box speeded up.
3) The box moved at constant speed.
Q6.3.c: You apply a force of < 0, 0, 5 > N to 1) W = 15 J
a box for 3 seconds. How much work did
2) W = 5 J
you do on the box?
3) W = 3 J
4) W = 5/3 J
5) Not enough
information.
Q6.3.d
A figure skater slides in the –x direction along
the ice, toward her partner. When she gets
close he pushes on her in the +x direction, to
slow her down. Does he do positive, negative,
or zero work?
∆r
F
1) positive
2) negative
3) zero
Q6.3.e
A fancart moves in the –x direction. The
1) positive
fan is on, and the force on the cart by the 2) negative
air is also in the –x direction. Is the work 3) zero
done by the air positive, negative, or zero?
∆r
F
Q6.3.f
A skater on a skateboard coasts in the +x
1) positive
direction. He is about to run into his friend, so 2) negative
she pushes him in the –x direction, to slow him 3) zero
down. What is the sign of the work done by the
friend?
∆r
F
Q6.3.g: A tennis ball is moving in
the –y direction. You hit it
downward with a tennis racket.
During the time your racket is in
contact with the ball, do you do
positive, negative, or zero work
on the ball?
∆r
F
1) positive
2) negative
3) zero
Q6.3.h
You move an object from
< 3, 7, 4 > m to < 2, 10, 12 > m,
applying a force < 10, –20, 30 > N
How much work do you do?
1) 10 J
2) 170 J
3) < -10, -60, 240 > J
4) < 30, -140, 120 > J
5) (− 10)2 + (− 60)2 + (240)2 J
Q6.3.i
You drop a ball of mass m at a height h
above the ground. The ball falls,
speeding up, bounces off the floor, and
goes upward, slowing down, until it is
once again at the location where you
released it (height h).
Initial state: Just after release
Final state: Ball back at original location
How much work was
done by the Earth on
the ball?
1) mgh
2) –mgh
3) 2*mgh
4) –2*mgh
5) 0
Q6.5.a: An isolated neutron decays: n → p + + e − + ν
Initial: Neutron at rest Final: p + , e − , and ν far from each other
1) The sum of the rest energies of the products equals the
rest energy of the neutron
2) The sum of the kinetic energies of the products equals the rest
energy of the neutron
3) The sum of the rest energies and kinetic energies of the products
equals the rest energy of the neutron
4) The sum of the kinetic energies of the products equals the
kinetic energy of the neutron
Q6.5.b: An isolated neutron decays: n → p + + e − + ν
Initial: Neutron at rest
Final: p + , e − , and ν far from each other
System: All particles
Energy principle: Ef = Ei + W
What quantities are included in the initial energy Ei?
A: Kn
C: Ke
E: mnc2
G: mec2
B: Kp
D: Kν
F: mpc2
H: mνc2
1) A
2) A, E
3) A, B, C, D
4) E, F, G, H
5) A, F, G, H
Q6.5.c: An isolated neutron decays: n → p + + e − + ν
Initial: Neutron at rest
Final: p + , e − , and ν far from each other
System: All particles
Energy principle: Ef = Ei + W
What quantities are included in the final energy Ef?
A: Kn
C: Ke
E: mnc2
G: mec2
B: Kp
D: Kν
F: mpc2
H: mνc2
1) A, C, E, G
2) B, C, D, F, G, H
3) A, E 4) B, C, D 5) E, F, G
Q6.7.a:
You push a crate out of a carpeted room and along a tiled hallway.
While on the carpet you exert a force of 30 N and the crate moves 2 m.
While on the tile you exert a force of 12 N and the crate moves 8 m.
How much work do you do?
1) 210 J
2) 180 J
3) 156 J
4) 105 J
5) 42 J
6) We need to know the mass of the crate.
Q6.7.b
A horizontal spring has stiffness 100 N/m.
A block is pressed against the spring,
compressing the spring 0.2 m, and then
released. When the spring has reached its
relaxed length, how much work will it have
done on the block?
1) 20 J
2) 4 J
3) 2 J
4) 0 J
5) We need to know
the mass of the block
Q6.8.a
A thrown ball heads straight up.
SYSTEM: Ball
What is the work done by
the surroundings?
1) 0
2) mg∆y
3) –mg∆y
4) something else
Q6.8.b
A thrown ball heads straight up.
SYSTEM: Ball + Earth
What is the work done by
the surroundings?
1) 0
2) mg∆y
3) –mg∆y
4) something else
Q6.8.c
A thrown ball heads straight up.
SYSTEM: Ball + Earth
How did the kinetic
energy of the system
change?
1) ∆K > 0
2) ∆K = 0
3) ∆K < 0
Q6.8.d
A ball of mass 0.1 kg is dropped
from rest near the Earth.
The ball travels downward 2 m,
speeding up.
SYSTEM: Ball
What is the work done by
the surroundings?
1) 0
2) + 1.96 J
3) – 1.96 J
Q6.8.e
A ball of mass 0.1 kg is dropped
from rest near the Earth.
The ball travels downward 2 m,
speeding up.
SYSTEM: Ball + Earth
What is the work done by
the surroundings?
1) 0
2) + 1.96 J
3) – 1.96 J
Q6.8.f
A ball of mass 0.1 kg is dropped
from rest near the Earth.
The ball travels downward 2 m,
speeding up.
SYSTEM: Ball + Earth
Work done by surroundings: 0
However, did the kinetic
energy of the Ball + Earth
system change?
1) K increased
2) K decreased
3) K did not change
For the system of Ball + Earth, ∆K > 0 but W = 0. We have a problem...
Q6.9.a
A spacecraft travels from near the
Earth toward the Moon. How many
gravitational potential energy terms
Ug are there in the Energy Principle?
System: Earth, Moon, spacecraft
1) 1
2) 2
3) 3
4) 6
5) 0
Q6.11.a:
Which of the following graphs of U vs r represents the
gravitational potential energy, U = –GMm/r?
Q6.11.b: In which graph does the cyan line correctly represent the
sum of kinetic energy plus potential energy?
1) A
2) B
3) C
Q6.12.a
A comet orbits a star in a
strongly elliptical orbit. The
comet and star are far from other
massive objects.
System: comet + star
The system has:
1) kinetic energy
2) kinetic energy and rest
energy
3) kinetic energy, rest
energy, and potential
energy
Q6.12.b
System: comet + star
As the comet travels away
from the star, how does
the kinetic energy and
potential energy of the
system change?
1)
2)
3)
4)
5)
K
increase
increase
decrease
decrease
no change
U
decrease
increase
increase
decrease
no change
Q6.12.c: A robot spacecraft leaves an asteroid. SYSTEM: craft + asteroid
Which quantities are the same in the initial state and the final state
(that is, which quantities do not change significantly, for this system)?
1) rest energy of asteroid, rest energy of spacecraft
2) rest energy of asteroid, rest energy of spacecraft, and
kinetic energy of asteroid
3) rest energy of asteroid, rest energy of spacecraft, and
gravitational potential energy
4) rest energy of asteroid, rest energy of spacecraft, and
kinetic energy of asteroid, and gravitational potential energy
Q6.12.d:
The system is a comet and a star. In which case(s) will the
comet escape from the star and never return?
1) A
2) B
3) C
4) A,B
5) B,C
6) A,B,C
Q6.14.a
Jack pulls to the left on a
Which forces are
positive charge, while Jill pulls
external?
to the right on a negative charge.
System: both charges
1) F1 and F2
2) F2 and F3
3) F3 and F4
4) F1 and F4
Q6.14.b
The charges are displaced, then
remain at rest.
System: both charges
The work done by
external forces was:
1) positive
2) negative
3) zero
4) need more information
Q6.14.c
System: both charges
Initial state: charges at rest
Final state: charges at rest,
farther apart
The positive work done
by external forces:
1) increased K of the
system
2) decreased K of the
system
3) did not change K of
the system
Q6.14.d
y-axis: energy; x-axis: separation
Which graph correctly shows U for a proton and an electron?
5: none of the above
Q6.14.e
y-axis: energy; x-axis: separation
Which graph correctly shows U for two interacting protons?
5: none of the above
Q6.14.f Two electrons, initially far apart, heading toward each other.
Same initial speed v. How close do they get before stopping?
K1f + K2f + Uf = K1i + K2i + Ui + W
Which terms are NOT zero?
1) K1f , K2f
4) Ui
2) Uf
5)K1f , K2f, Ui
3) K1i , K2i
6) K1i , K2i, Uf
Q6.14.g
Two electrons, initially far apart,
heading toward each other.
By applying the energy principle we
found that:
Uf = K1,i + K2,i
Which term contains the distance
of closest approach?
1) Uel,f
2) K1,i
3)K2,i
4) None of the above
Q6.14.h
y-axis: energy; x-axis: separation
Which graph shows K, U, and K+U for the two interacting electrons?
5: none of the above
Q6.17.a: alpha + carbon => oxygen + photon
What is the minimum initial kinetic energy of the alpha particle?
mOc2 + KO + Eγ = mαc2 + mCc2 + Kα + Kc + Ui
1
2
3
4
Which term contains the unknown?
5
6
7
8
Q6.17.b: alpha + carbon => alpha + carbon just barely touching each other
What is the minimum initial kinetic energy of the alpha particle?
U f = Kα + K c
1
2
3
Which term contains the unknown?