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Physics of Everyday Phenomena
W. Thomas Griffith
Juliet W. Brosing
Chapter 7
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Question 7.1
If the momentum of an object is doubled, its
speed must have increased by
A) 4
B) 2
C) 0.5
D) 0.25
Question 7.2
An 18-wheeler and a Volkswagon Beetle are
rolling along with the same momentum.
Which one is going faster?
A) 18-wheeler
B) Volkswagon beetle
C) same for both
D) impossible to say
Question 7.3
Maggie drops a stuffed bear over the side of
her crib. It hits the floor with speed v and
comes to rest. She then drops a rubber ball
with the same mass from the same height,
and it bounces back upwards with speed v.
Compare the change in momentum of the
bear and the ball.
A) Dpbear = Dpball
B) Dpbear = 2 Dpball
C) Dpbear = ½ Dpball
D) Dpbear = - Dpball
Question 7.4
An 18-wheeler and a Volkswagon Beetle are
rolling along with the same momentum. If
you exert the same force with the brakes to
stop each one, which takes a longer time to
bring to rest?
A) 18-wheeler
B) Volkswagon beetle
C) same for both
D) impossible to say
Question 7.5
Red Rover, Red Rover, let Leslie come over. In
this childhood game, you try to stop and catch
a person who is running directly at you. Who
would you rather pick?
A) Sean, who weighs 350 N and can run
5 m/s.
B) Meihong, who weighs 250 N and can run
8 m/s.
C) Deidra, who weighs 300 N and can run
3 m/s.
Question 7.6
An urban legend has it that the RAF was
testing the windshields of their aircraft for
bird strikes using a chicken cannon given to
them by the USAF. The windshields kept
breaking because they were using frozen
chickens instead of fresh ones. Using your
knowledge of physics, you would reason
that the legend is
A) false - frozen and thawed chickens have
the same momentum on impact.
B) true - frozen chickens are harder and
come to rest in a shorter time,
increasing the force.
Question 7.7
An astronaut is taking a space walk when his
tether breaks. He has a big drill. How can he
get back to the space ship?
A) Turn his back to the ship
and throw the drill forward
B) Face the ship and
throw the drill forward.
C) Throw the drill towards
the tether.
Question 7.8
As a kid playing on the playground, you would bend your knees
when you landed after jumping off the monkey bars to reduce
the "sting" in your feet. This worked because
A) bending your knees gave you upward
momentum which partly canceled the downward
momentum.
B) bending your knees lowered your center of
gravity reducing the force of your fall.
C) bending your knees increased the time of
contact for the ground to bring you to rest.
D) you didn't do it on purpose, your knees just
buckled.
Question 7.9
Two forces produce equal impulses, but the
second force, F2, acts for a time twice that of
the first force, F1. Which force, if either, is
larger?
A) F1
B) they are the same
C) F2
Question 7.10
The principle of conservation of momentum
A) is valid only for perfectly inelastic collisions
B) is valid only for perfectly elastic collisions
C) is valid for all collisions
D) is valid only if the net external force acting on
the system is zero
E) states that it is impossible to change the
momentum of an object
Question 7.11
An innocent mosquito is flying along the
interstate and has a collision with a
speeding semi. Which one feels a greater
force?
A) The mosquito
B) The semi
C) They both feel the same force
D) There are no forces involved
Question 7.12
An innocent mosquito is flying along the
interstate and has a collision with a
speeding semi. Which one experiences a
greater change in momentum?
A) The mosquito
B) The semi
C) They both experience the same change in
momentum
D) There is no change in momentum
Question 7.13
An innocent mosquito is flying along the
interstate and has a collision with a
speeding semi. Which one experiences a
greater acceleration (change in velocity)?
A) The mosquito
B) The semi
C) They both experience the same
acceleration
D) There is no change in velocity
Question 7.14
An collision occurs between object X and
object Z. Object X has twice the mass of
object Z. Which of the following quantities is
NOT the same for the two objects?
A) Magnitude of change in momentum
B) Magnitude of force felt by each
C) Time of collision
D) Magnitude of change in velocity
Question 7.15
These two skaters have just pushed off against
one another. One skater has twice the
mass as the other. Which one will
experience the greater momentum?
A) The heavier skater
B) The lighter skater
C) Neither, they both
have the same
Question 7.16
These two skaters have just pushed off against
one another. One skater has twice the
mass as the other. Which one will
experience the greater velocity?
A) The heavier skater
B) The lighter skater
C) Neither, they both
have the same
Question 7.17
Why is the recoil less if a person holds a gun tightly
against the shoulder?
A)
The recoil is not less. Since momentum is
conserved, the recoil is the same whether or not
the gun is held tightly
B)
Your mass becomes part of the system, and since
momentum is conserved, the velocity of the
gun/person system is reduced
C) If the gun is held tightly the bullet doesn’t travel as
fast so conservation of momentum leads to a
smaller recoil velocity of the gun.
Question 7.18
An airplane propeller pushes against the air, and the
air, by Newton’s 3rd law, pushes against the
propeller. How does a rocket work in outer space
where there is no atmosphere?
A)
There is enough atmosphere, even in outer space,
for the same principle to work.
B)
A rocket exerts a force on its exhaust gases and
the gases exert a force on the rocket.
C) Rockets use nuclear power and don’t need an
atmosphere to work.
Question 7.19
In which type of collision do the objects stick
together afterwards?
A) A perfectly elastic collision
B) A perfectly inelastic collision
C) A partially inelastic collision
Question 7.20
In which type of collision is no kinetic energy
lost?
A)
B)
C)
D)
A perfectly elastic collision
A perfectly inelastic collision
A partially inelastic collision
Energy is always conserved
Question 7.21
In which type of collision is the most kinetic
energy lost?
A) A perfectly elastic collision
B) A perfectly inelastic collision
C) A partially inelastic collision
D) Kinetic energy is always conserved
Question 7.22
A 280-lb linebacker running down the field at 7
m/s tackles a 240-lb halfback running up
the field at 9 m/s. Will the halfback gain or
lose yards after he is tackled?
A) gain
B) lose
C) neither gain nor lose
Question 7.23
Wire, briar, limber, lock, three geese in a flock.
One flew east, one flew west, and one flew
over the cuckoo's nest. If they all flew at the
same speed and the cuckoo's nest is to the
northwest, which graph represents their total
momentum?
A)
B)
C)
Question 7.24
Two football players moving as shown, collide.
Which vector triangle represents their total
momentum before the collision?
A
B
C
Question 7.25
When playing pool or billiards, the paths of the
two balls after a collision are at
approximately right angles to one another.
This is due to:
A) The fact that momentum is conserved
B) The fact that kinetic energy is conserved
C) The fact that both momentum and kinetic
energy is conserved
Answer Key to Chapter 7
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
B
B
C
C
B
B
A
C
A
D
C
C
A
14)
15)
16)
17)
18)
19)
20)
21)
22)
23)
24)
25)
D
C
B
B
B
B
A
B
A
B
B
C