73 terms

# Physics

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The scientist to first introduce inertia:
Galileo
Hang from a pair of gym rings and the upward support forces of the rings will always
The force of friction on a sliding object is 10 N. The applied force needed to maintain a constant
velocity is
10N
A 300-kg bear grasping a vertical tree slides down at constant velocity. The friction force between the
tree and the bear is
3000N
The two measurements necessary for calculating average speed are
distance and time
A horse gallops a distance of 10 kilometers in a time of 30 minutes. Its average speed is
20 km/h
A car maintains a constant velocity of 100 km/hr for 10 seconds. During this interval its acceleration is
zero
In science, an educated guess is a
hypotheses
The synthesis of a large collection of information that contains well-tested and verified hypotheses
about certain aspects of the world is known as a scientific
theory
An object in mechanical equilibrium is an object
at rest
moving with constant velocity
having no acceleration
A truck is moving at constant velocity. Inside the storage compartment, a rock is dropped
from the midpoint of the ceiling and strikes the floor below. The rock hits the floor
exactly below the midpoint of the ceiling
A 1-kg mass at the Earth's surface weighs how many N?
9.8 N
A vehicle that weights 400 N on the surface of the Earth is traveling in outer space at a speed
of 400 m/s. It can be stopped by applying a constant force of 20 N for
800 seconds
It is correct to say that impulse is equal to
the change in momentum
The impulse-momentum relationship is a direct result of
Newton's 2nd law
The conservation of momentum is most closely related to
Newton's 3rd law
A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the
rifle has much more mass than the bullet
Suppose that a tiny gun made of a strong but very light material fires a bullet that is more
massive than the gun itself. For such a weapon
the target would be safer than the shooter
Two objects have the same size and shape, but one is much heavier than the other. When
they are dropped simultaneously from a tower, they reach the ground at the same time, but
the heavier one has a greater
momentum
To catch a ball, a baseball player extends the hand forward before impact with the ball and
then lets it ride backward in the direction of the ball's motion. Doing this reduces the force
of impact on the player's hand principally because the
time of impact is increased
Padded dashboards in cars are safer in an accident than non-padded ones because an occupant
hitting the dash has
increased time of impact
The force on an apple hitting the ground depends upon
the speed of the apple just before it hits.
the time of impact with the ground.
whether or not the apple bounces.
A 4 kg ball has a momentum of 12 kg m/s. What is the ball's speed?
3m/s
p = mv
p/m= v
v =12/4
= 3m/s
A karate expert executes a swift blow and breaks a cement block with her bare hand. The
magnitude of the force experienced by her hand is
identical to the force applied
Two billiard balls having the same mass and speed roll toward each other. What is their
combined momentum after they meet?
0
The power required to exert 1 N force, over a distance of 1 m in 1 second is
1W
When bullets are fired from an airplane in the forward direction, the momentum of the airplane
will be
decreased
Suppose the circumference of a bicycle wheel is 2 meters. If it rotates at 1 revolution per
second when you are riding the bicycle, then your speed will be
2 m/s
A broom is easier to balance on its end when the heavier end (the brush end) is
An industrial flywheel has a greater rotational inertia when most of its mass is
nearest the rim
A torque acting on an object tends to produce
rotation
On a balanced seesaw, a boy three times as heavy as his partner sits
1/3 the distance from the fulcrum
Put a pipe over the end of a wrench when trying to turn a stubborn nut on a bolt, to effectively
make the wrench handle twice as long, you'll multiply the torque by
2
Toss a baseball bat into the air and it wobbles about its
center of mass
The famous Leaning Tower of Pisa doesn't topple over because its center of gravity is
above a place of support
When a twirling ice skater brings her arms inward, her rotational speed
increases
For a system in mechanical equilibrium the resultant forces and torques
must both be zero.
A 1-kg rock is suspended from the tip of a meter stick at the 0-cm mark so that the meter
stick balances like a seesaw when the fulcrum is at the 25-cm mark. From this information,
what is the mass of the meter stick?
1kg
Suppose you roll a ball off a tabletop. Will the time to hit the floor depend on the speed of the ball?
No (because the vertical velocity is independent of the horizontal)
Suppose you roll a ball off a tabletop. Will the time to hit the floor depend on the speed of the ball?
Yes. (because the horizontal component of velocity combined with the vertical component results in a greater speed. That is why the ball travels a longer distance in the same amount of time)
If you toss a ball vertically upward in a uniformly moving train, it returns to its starting place. Will it do the same if the train is accelerating?
No (since the train is accelerating and the ball is moving at a constant velocity.)
A park ranger shoots a monkey hanging from a branch of a tree with a tranquilizing dart. The ranger aims directly at the monkey. The monkey lets go of the branch as soon as the ranger shoots. Will the monkey be hit?
yes
Which planets have a more than one Earth year period, planets nearer or farther from the sun?
planets farther form the sun
A circularly moving object requires a centripetal force. What supplies this force for satellites that orbit Earth?
gravity
Mars has about 1/9 the mass of Earth. If Mars were somehow positioned into the same orbit as Earth's, how would its time to circle the Sun compare with Earth's?
it would be the same
When an Earth satellite is placed into a higher orbit, what happens to its period?
increases
In an accidental explosion, a satellite breaks in half while in circular orbit about Earth. One half is brought momentarily to rest. What is the fate of half brought to rest? What happens to the other half?
the half brought to rest falls to Earth and the other half's velocity doubles
Science is a body of knowledge that
describes order in nature
is an ongoing activity of humans
condenses knowledge into testable laws
In science, facts
may change
Whereas Aristotle relied on logic in explaining nature, Galileo relied on
experiment
When you stand at rest on a pair of bathroom scales, the readings on the scales will always
Acceleration equals
velocity and time
If no external forces are acting on a moving object it will
continue moving at the same velocity
While an object near the Earth's surface is in free fall, its velocity
increases
A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected the force required to keep the puck sliding at constant velocity is
zero
If a freely falling object were somehow equipped with a speedometer on a planet where the acceleration due to gravity is 20 m/s/s, then its speed reading would increase each second by
20 m/s
If an object moves with constant acceleration its velocity must
change by the same amount each second
An 80 kg mass at the Earth's surface weighs how many N?
800 N
In which case would you have the largest mass of gold? If your chunk of gold weighed 1 N on the moon, Earth, or Jupiter
moon
Weight is expressed in units of
Newtons
A 10 kg brick and a 1 kg book are dropped in a vacuum. The force of gravity on the 10 kg brick is
10 times as much
An astronaut, floating alone in outer space throws a baseball. If the ball floats away at a peed of 20 m /s the astronaut will
move in the opposite direction but at a lower speed
If a monkey floating in outer space throws hi hat away, the hat and the monkey will both
move away from each other but at different speeds
A 1 kg glider and a 2 kg glider both slide toward each other at 1 m/s on an air track. They collide and stick. The combined mass moves at
1/3 m/s
Which requires the most amount of work by the brakes of car
slowing down from 100 km/h to 70 km/h
According to Newton, doubling the distance between two interacting objects
divides by 4 the gravitational force between them
What is the force of gravity on a 500- N woman standing on the Earth's surface
500 N
Inside a freely falling elevator, there would be no
apparent weight for you
An asteroid exerts a 360 N gravitational force on a nearby spacecraft. If the spacecraft moves to a position three times as far from the center of the asteroid, the force will be
40 N
An object is placed exactly halfway between the Earth and the moon. The object will fall toward
Earth
The amount of gravitational force that acts on the space shuttle while in orbit is
almost as much as the shuttle's weight on the Earth's surface
A stone is thrown horizontally from the top of a cliff. One second after it has left your hand, its vertical distance below the top of the cliff is
5m
Earth satellites are typically more than 100 km high so as to be above the Earth's
atmosphere