48 terms

Physics exam 3 review

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The law of inertia states that an object
-will continue moving at the same velocity unless an outside force acts on it.
-will continue moving in a straight line unless an outside force acts on it.
-that is not moving will never move unless a force acts on it.
-at rest will remain at rest unless acted on by an outside force.
The law of inertia applies to
both moving and nonmoving objects.
According to Newton's third law, if you push gently on something, it will push
gently on you.
In physics, work is defined as
force times distance.
If Nellie Newton pushes an object with twice the force for twice the distance, she does
four times the work.
The unit of work is the
joule.
Power is defined as the
work done on an object divided by the time taken to do the work.
The unit of power is the
watt.
Potential energy is the energy an object has because of its
location.
Kinetic energy of an object is equal to
one half the product of its mass times its speed squared.
How much farther will a car traveling at 100 km/s skid than the same car traveling at 50 km/s?
Four times as far.
As a pendulum swings back and forth
-at the end points of its swing, its energy is all potential.
-at the lowest part of its swing, its energy is all kinetic.
-kinetic energy is transformed into potential energy.
-potential energy is transformed into kinetic energy.
An object that has kinetic energy must have
momentum.
A person on a roof throws one ball downward and an identical ball upward at the same speed. The ball thrown downward hits the ground with 140 J of kinetic energy. Ignoring air friction, with how much kinetic energy does the second ball hit the ground?
140 J
A heavy object and a light object are released from rest at the same height and time in a vacuum. As they fall, they have equal
Nothing
All simple machines ideally work on the principle that
work input equals work output.
About how efficient is a typical gasoline-burning car engine?
30%
How many joules of work are done on a box when a force of 25 N pushes it 3 m?
75 J
The momentum of an object is defined as the object's
mass times its velocity.
Which has more momentum, a large truck moving at 30 miles per hour or a small truck moving at 30 miles per hour?
The large truck
If the momentum of an object changes and its mass remains constant,
-it is accelerating (or decelerating).
-there is a force acting on it.
-its velocity is changing.
The momentum change of an object is equal to the
impulse acting on it.
In order to increase the final momentum of a golf ball, we could
-increase the force acting on it.
-follow through when hitting the ball.
-increase the time of contact with the ball.
-swing as hard as possible.
The reason padded dashboards are used in cars is that they
increase the time of impact in a collision.
A collision is considered elastic if
-there is no lasting deformation.
-the objects don't stick together.
-the objects that collide don't get warmer.
-after the collision, the objects have the same shape as before the collision.
Suppose a girl is standing on a pond where there is no friction between her feet and the ice. In order to get off the ice, she can
throw something in the direction opposite to the way she wants to go.
A cannon recoils from launching a cannonball. The speed of the cannon's recoil is small because the
cannon has far more mass than the cannonball.
Suppose a cannon is made of a strong but very light material. Suppose also that the cannonball is more massive than the cannon itself. For such a system
the target would be a safer place than where the operator is located.
In order to catch a ball, a baseball player moves his or her hand 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.
After a cannonball is fired into frictionless space, the amount of force needed to keep it going equals
zero, since no force is necessary to keep it moving.
Which has more mass, a kilogram of feathers or a kilogram of iron?
Neither—they both have the same mass.
You and a friend are jumping on a trampoline. Why does Earth, which is rapidly orbiting around the sun, not move under your feet when you jump?
Newton's first law holds that your body moves along with Earth because it is not compelled to change its motion by an unbalanced force.
Accelerations are produced by
forces
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 as the force on the 1-kg book.
A book weighs 4 N. When held at rest in your hands, the net force on the book is
0 N.
A tennis ball and a solid steel ball with the same diameter are dropped at the same time. Which ball has the greater force acting on it?
The steel ball
A tennis ball and a solid steel ball with the same diameter are dropped at the same time. In the absence of air resistance, which ball has the greater acceleration?
They both have the same acceleration.
The reason a tennis ball and a solid steel ball will accelerate at the same rate, in the absence of air resistance, is that
the ball with the larger force also has the larger mass.
Whenever an object exerts a force on another object, the second object exerts a force of the same magnitude, but in the opposite direction to that of the first object
Always true
In the absence of air friction, the vertical component of a projectile's velocity doesn't change as the projectile moves.
Always false
In the absence of air friction, the horizontal component of a projectile's velocity doesn't change as the projectile moves.
Always true
At the instant a ball is thrown horizontally with a large force, an identical ball is dropped from the same height. Which ball hits the ground first?
Neither. They both hit the ground at the same time.
A ball is thrown into the air at some angle. At the very top of the ball's path, its velocity is
entirely horizontal.
In the absence of air resistance, the angle at which a thrown ball will go the farthest is
45%
A projectile launched horizontally hits the ground in 0.8 seconds. If it had been launched with a much higher speed in the same direction, it would have hit the ground (neglecting Earth's curvature and air resistance) in
0.8 s
An object is dropped and falls freely to the ground with an acceleration of g. If it is thrown upward at an angle instead, its acceleration would be
g downward
A baseball is hurled into the air at an angle of 30 degrees above the horizontal and lands on a target that is at the same level as that where the baseball started. The baseball will also land on the target if it is thrown at an angle of
60%
In the absence of air resistance, at what other angle will a thrown ball go the same distance as one thrown at an angle of 75 degrees?
15%