Chapter 1-4 pretest
A motor scooter undergoes acceleration when it
gains speed, decreases speed, changes direction.
According to Newton, the greater the masses of interacting objects, the
greater the gravitational force between them.
A ball rests in the middle of a cart. When you quickly jerk the cart forward, the ball
hits the back of the cart
An object that has twice as much mass as another object also has twice as much
inertia
Compared with a 1-kg block of solid iron, a 2-kg block of solid iron has twice as much
inertia, mass and volume
You toss a ball upward where air resistance is negligible. After the ball leaves your hand the force on it
is the single force due to gravity, always directed downward
An object in motion will continue in motion with
momentum
According to Newton, the closer gravitationally interacting objects are to each other, the
more the gravitational force between them.
An object that has kinetic energy must be
moving.
Which requires more work on the brakes of a car?
slowing down from 100 km/h to 70 km/h
From the same height you simultaneously drop a lightweight tennis ball and a heavyweight bowling ball. When they hit the floor they have the same
speed
The circular orbit of a satellite orbiting the Earth is characterized by a constant
speed, acceleration, radial distance
A moving object has
speed, velocity, momentum, energy
Newton discovered
that gravity is universal.
When you push your desk to the right, friction on the desk acts toward
the left
Compared with the mass of a certain object on Earth, the mass of the same object on the Moon is
the same
A ball is thrown upwards and caught when it returns. Neglecting air resistance, the speed with which it is caught is
the same as its initial speed.
The distinction between impulse and force involves the
time the force acts.
An Earth satellite is simply a projectile freely falling around the Earth.
true
If you push an object twice as far while applying the same force, you do
twice as much work.
If you do work on an object in half the time, your power output is
twice.
Inside a freely falling elevator your
weight is zero.
The speed of a vertically-thrown ball at the top of its path is
zero
The ultimate source of energy from fossil fuels is the
Sun.
In terms of momentum, why is a drinking glass less likely to break if it falls on a carpet floor than falling on a hard concrete floor?
The carpet has more "give" so it takes more time to change the momentum, which means it less force and less chance of breaking.
You do work on an object when you lift it against gravity. How does this work relate to gravitational potential energy? If the lifted body is dropped, what becomes of this energy?
The work you do lifting the box is stored as gravitational potential energy. If the box is dropped the gravitational potential energy is transformed into kinetic energy.
A machine puts out 100 W of power for every 1000 W put into it. The efficiency of the machine is
10%.
If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by about
10 m/s
Two billiard balls having the same mass roll toward each other at the same speed. What is the net momentum of the two-ball system?
0 kg∙m/s
It takes 40 J to push a large crate 4 m across a floor. The force exerted on the crate is
10 N.
What is the meaning of the expression ΣF = 0?
It is the mathematical expression of the Equilibrium Rule - The sum of all forces equals zero.
Distinguish between the concepts of mass and weight. Which is more fundamental, and why?
Mass is a quantity of matter in an object and is more fundamental. Mass involves only the object. Weight is mass times the acceleration due to gravity and depends on object's location.
The impulse-momentum relationship is a direct result of
Newton's second law.
Action and reaction forces comprise the parts of
a single interaction
If the mass of an object does not change, a constant net force on the object produces constant
acceleration
Newton's second law directly involves
acceleration
Which has zero acceleration?
an object at rest, an object moving at constant velocity, an object in mechanical equilibrium.
An archer shoots an arrow. If the action force is the bowstring on the arrow, the reaction is the
arrow's push on the bowstring
A bullet fired from a rifle begins to fall
as soon as it leaves the barrel.
An object in mechanical equilibrium is an object
at rest, moving at constant velocity, with no acceleration.
A rock is thrown upward at 50° with respect to the horizontal. As it rises, its vertical component of velocity
decreases.
An open freight car rolls friction-free along a horizontal track in vertically pouring rain. As water accumulates in the car, its speed
decreases.
The two measurements necessary for calculating average speed are
distance and time
Whereas impulse involves the time that a force acts, work involves the
distance that a force acts.
A popular swinging-balls apparatus (Newton's cradle) consists of a series of identical elastic balls suspended by strings so they barely touch each other. When two balls are pulled away from one end and released, they strike the row of balls and two balls pop out from the other end. If instead, one ball popped out with twice the speed, this would be a violation of conservation of
energy.
A simple machine CANNOT multiply
energy.
The force that accelerates a rocket in outer space is exerted on the rocket by the
exhaust gases.
In contrast to Aristotle's way of explaining nature, Galileo relied on
experiment
Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the rock tends to
follow a straight-line path
Two identical arrows, one with twice the speed of the other are fired into a bale of hay. The faster arrow will penetrate the bale
four times as far as the slower arrow.
