The distance a freely falling object falls from rest in three seconds here on earth is
45 m. d = 1/2a(t^2)
The first estimate of the size of the Moon and the first written record for the Sun-centered cosmos are attributed to
Aristarchus.
What is the significance of the famous Apple Story that is associated with Isaac Newton?
It was Newton's genius to connect the physics that explains why the apples falls under the force of gravity is the same physics that explains why the moon orbits or why the international space station orbits the earth-- it is in free fall.
Nellie pulls with a force of 20 N on a horizontal rope tied to a tree at rest. The net force on the rope is
zero and rope tension is 20 N. (net force is zero because the tree pulls with a force of 20 N also)
If air resistance is neglected, a stone dropped from the roof of a single story building to the surface of the earth
speeds up because of an almost constant force of gravity acting upon it.
Your physics teacher fired a steel ball with a velocity of 3 m/s in the horizontal direction. At the same time she dropped a similar steel ball from the same height. Which on hit the ground first and why? Neglect air resistance.
They both hit the ground at the same time as the force of gravity is the same for both and only acts in the vertical direction.
A kilogram is a measure of an object's
mass.
When you flick a card from beneath a coin that hardly moves, you're illustrating
inertia.
Whenever the net force on an object is zero, it's acceleration is
zero.
The Greek mathematician Eratosthenes made observations of sunlight striking water in the bottom of a well and shadows casting in a neighboring town to find the size of
Earth.
A motorboat that normally travels 40 km/h in still water heads directly across a 30 km/h flowing river. The resulting speed of the boat is about
50 km/h. (using the Pythagorean Theorem, 40^2 + 30^2 = 2500. Taking the square root of 2500 gives us 50)
The force that propels a cannonball when fired from a cannon is
equal and opposite to the force the ball exerts on the cannon.
When a cannon is fired from a cannon, which undergoes the greater acceleration?
The cannonball
You toss a ball upward with an initial velocity of 30 m/s. Neglecting air resistance, after 3 seconds you find that
the velocity is zero and the acceleration is 10 m/s/s downward.
Which of the following is NOT a characteristic of a scientific hypothesis? A) there must be a doable test for wrongness B) once proved correctly by one experiment, it can never be proven wrong by any experiment C) it is only presumed to be factual after supported by experiment D) it is an educated guess
B) once proved correctly by one experiment, it can never be proven wrong by any experiment
An 800 N man stands at rest on two bathroom scales so that his weight is distributed evenly over both scales. The reading on each scale is
400 N.
Galileo discovered that when air resistance can be neglected, all objects fall with the same
acceleration due to gravity
The weight of a full jug of water (like a Smartwater bottle) on the surface of the moon is
less than it is here on the surface of Earth.
A ball starting from rest at the top of an inclined plane accelerates at 4 m/s/s and reaches the bottom of the plane in 6 seconds. What is the length of the plane?
72 m. d = 1/2a(t^2)
What is an example of Aristotelian thinking?
Heavy objects are hard to move and come to rest quickly. Earth is so heavy it does not move and is consequently stationary at the center of the cosmos.
Galileo taught us that if you roll a ball along a level surface it will
keep rolling if friction is absence.
You toss a ball and it makes a curved path. At the instant that the ball leaves your hand it has a velocity which gas a horizontal component of 40 m/s and a vertical component of 20 m/s. How far from you does the ball land? Neglect air resistance.
160 m.
Suzie Skydiver jumps from a high-flying plane. As her velocity of fall increases, her acceleration
decreases.
If a freely falling object were equipped with a speedometer on a planet where the acceleration due to gravity is 60 m/s/s, then its speed reading would increase each second by
60 m/s.
The time it takes a car to attain a speed of 100 m/s when accelerating from rest at 5 m/s/s is
20 s. V(final) = V(initial)+ at 100 m/s = (0 m/s) + (5 m/s/s)t t = (100 m/s) / (5 m/s/s)
Two metal balls are the same size but one weighs twice as much as the other. The balls are dropped from the roof of a single story building at the same instant of time. Neglect air resistance. The time it takes the balls to reach the ground below will be
about the same for both balls.
Consider a rocket set to launch on a launch pad. When a rocket forces exhaust gases downward, the exhaust gases
exert an upward force on the rocket.
A 2 kilogram block is pushed across a horizontal surface with a horizontal force of 20 N against a friction force of 10 N. The acceleration of the block is
5 m/s/s. F(net) = ma 20 N -10 N = (2 kg)a a = 10/N / 2 kg
A woman exerts a constant horizontal force on a large box. As a result, the box moves across a horizontal floor at a constant speed of v0. The constant horizontal force applied by the woman
has the same magnitude as the total force which resists the motion of the box.
A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always
directed downward.
A 3 kg mass at the Earth's surface weighs
30 N.
An object's weight is properly expressed in units of
newton's.
A watermelon falls off a truck that is moving at 60 mph. Neglecting air resistance, the horizontal speed of the melon just before it hits the ground is
about 60 mph.
A river 50 m wide flows due south at 1 m/s. A boat that travels 1 m/s relative to the water is pointed due east as it crosses from the west bank. The boat reaches the east bank
50 m farther south.
A skydiver jumps from a plane and deploys a parachute. When the skydiver reaches terminal velocity, the magnitude of the forces that is the weight of the skydiver
is equal in magnitude to the forces of the air drag but in the opposite direction.
In Physics we seek
to describe nature and understand its rules.
A light woman and a heavy man jump from an airplane at the same time and open their same-size parachutes at the same time. Which person will get to the state of zero acceleration first?
The light woman
A wheel rotates with an angular speed of 6 radians per second and it has a radius of 2 meters. What is the linear speed of a bug located on the outer radius of this wheel?
12 m/s v = rw
A seesaw is balanced with the fulcrum at its midpoint. If a 3 kg weight is placed one meter from the fulcrum on one side, where would you need to place a 6 kg weight on the opposite side in order to balance the seesaw again?
One half meter from the fulcrum.
A cannon recoils while firing a cannonball. The speed of the cannon's recoil is relatively small because the
cannon has much more mass than the cannonball.
A simple machine like a pulley may do all of the following EXCEPT: A) create energy B) change the direction of forces exerted C) can reuce the amount of force required to lift an object D) transform energy from one kind to another
A) create energy
As a huge rotating cloud of particles in space gravitate together forming an increasingly dense ball, it shrinks in size and
rotates faster.
Whether a truck come to a stop by crashing into a haystack or a brick wall, the impulse is
both the same.
A 6 W LED produces the same amount of light as a 60 W incandescent light bulb. If both are left on for one day we find that
the LED uses one tenth the energy as compared to the incandescent bulb and produces the same light because it is more efficient.
Compared with falling on a stone floor, a wine glass may not break when it falls on a carpeted floor because the
stopping time is longer on the carpet.
The power required to exert a 5 N force over 4 meters in 2 seconds is
10 W Power = work/time
The momentum of a system will remain unchanged
only if you choose the system so that there are no external forces acting on it. All action/reaction forces are acting on objects inside the system.
If several balls are thrown straight up with different initial speeds, the quantity that will have the same value along their paths is their
acceleration.
Centrifugal forces are
apparent forces caused by inertia that feels like a radially outward force.
Which of the following are considered greenhouse gases? A) molecular oxygen/nitrogen B) atomic hydrogen/helium C) carbon dioxide and water vapor D) argon and neon
C) carbon dioxide and water vapor
A light aluminum ball and a heavy lead ball of the same size roll down an incline. When they are halfway down the incline, they heavy lead ball will have greater
kinetic energies, inertias, potential energies, and momentum
A round stone of mass 2 kg is dropped off a bridge over a river and falls for 2 seconds before reaching the water. Its momentum upon hitting the water is
40 kg m/s p=mv = (2 kg)(10m/s/s * 2s)
An impulse can be increased by
increasing the force and/or increasing the time interval.
Two identical space crafts move at different speeds. The faster craft has four times the speed and therefore has
sixteen times the kinetic energy. KE = 1/2m(v^2) = 1/2m(4v^2) = 1/2m16(v^2)
A force acts on an object for a period of time and sets it in motion. Which of the following is TRUE? The force multiplied by the time is ________ and the force multiplied by the distance is ________
the impulse or change in momentum, the work done by the force
No work is done by gravity on a bowling ball that rolls along a bowling alley because
the force on the ball is at a right angle to the ball's motion.
Two object have the same mass and radius. One is a hoop and the other is a solid cylinder. If you race the 2 objects down an incline, neglecting air resistance, which do you expect to reach the bottom of the incline first?
The solid cylinder because it has a lower rotational inertia and so it will have the greater acceleration.
The mass of a big fish is four times that a little fish. The speed of the little fish is 5 km/hr and the big fish is at rest. If the little fish swims into the mouth of the big fish, what is the speed of the big fish after his fish dinner?
1 km/hr (net mv)before = (net mv)after 1 kg * 5 km/hr = 5 kg * v
What does it mean for a gas to be a green house gas?
The gas is in the atmosphere and it strongly absorbs infrared radiation.
The mass of a ball moving at 12 m/s with a momentum of 48 kg m/s is
4 kg p=mv 48 kg m/s = 12 m/s * m m= 48 kg m/s / 12 m/s
An apple falls from a tree from a height of 3 meters. The weight of the apple is 1 N . What is the kinetic energy of the apple just before it hits the ground?
3 J KE = F(net) * d KE = 1 N * 3 m
In considering the work energy theorem, when negative net work is done on an object, we find
the object slows down.
Rotational Inertia depends upon
the mass of the object and the distribution of the mass about the axis of rotation.
An apple has a weight of 1 N at the surface of the Earth. What is the weight of the apple if it was not at the surface, but rather at one earth radii above the surface?
1/4 N
Whether a truck comes to a stop by crashing into a haystack or a brick wall, the stopping force is
greater with the brick force.
When a vertically falling firecracker bursts, the vector sum of momentum fragments
in the vertical direction equals the momentum of the firecracker before bursting and in the horizontal direction cancels to zero.
A blue railroad car of mass m rolls at a certain speed and makes a perfectly inelastic collision with an orange car that has twice the mass and is at rest. After the collision, what is the speed of the coupled cars?
One third the speed of the blue car before collision.
The famous Leaning Tower of Pisa doesn't topple over because its center of gravity is
above a place of support.
If you triple your speed, how does that change your stopping distance if all other conditions remain the same? Do not consider reaction time.
The stopping distance is 9 times as long.
In considering the work-energy theorem, the work done on an object by a net force is always
equal to the objects change in kinetic energy.
Two billiards balls having the same mass and speed roll toward each other. What is their combined momentum after they meet?
Zero
If you exert a net torque on an object, you will find that
the object may speed up or slow down it's rotation rate.
The unit kilowatt-hour is a unit of
energy.
What is the physics behind the greenhouse effect?
The Sun warms the ground which causes the ground to radiate in infra-red wavelengths that are strongly absorbed by carbon dioxide and other green house gases, causing the lower atmosphere to warm.
A same-sized iron ball and wooden ball are dropped simultaneously from a tower and reach the ground at the same time. The iron ball has a greater
momentum.
Which of the following requires the most mechanical work? Lifting a (10 kg, 0.1 kg, 2 kg) sack a vertical distance of (1m, 50m, 2m).
Lifting a 10 kg sack a vertical distance of 1 m.
When an object is partly or wholly immersed in a liquid, it is buoyed up
by a force equal to the weight of liquid displaced.
Compared to the atoms that make up the body of an elderly person, the atoms that make up the body of a newborn baby are
the same age.
As a balloon rise higher and higher into the atmosphere its
volume increases.
Compared to a bar of pure gold, the density of a pure gold ring is
the same.
A spring is stretched 20 cm by a suspended 1 kg block. If two such springs side-by-side are used to suspend the 1-kg block, each spring will then stretch
10cm.
Why can we not use powerful optical microscopes using visible wavelengths to see individual atoms?
Atoms are much smaller than the wavelength of visible light.
What is Browian Motion?
Jiggling of dust particles in a liquid caused by unseen atoms interpreted as evidence for existence of atoms.
Where do naturally occurring elements heavier than boron come from?
They are made by stars in nuclear fusion and supernova events.
A block of wood that weighs 25 N is floating in a pond. Knowing this we also know
The weight of the water displaced by the floating block of wood is also 25 N.
Why do we say that a blob of putty is inelastic?
When deformed, it does not return to its original shape.
If an astronaut landed on a planet composed of antimatter, there would be an explosion and the
astronaut and an equal amount of planet antimatter would both annihilate.
If you have an unidentified atom, how do you tell which element the atom is? To identify the element that an atom is, count its number of
protons.
What is the magnitude of the Earth's gravitational force on a 3 kg rock at Earth's surface?
30 N
How does the arrangement of atoms in a crystalline substance differ from the arrangement in a noncrystalline (amorphous) substance.
Atoms in crystals are in an ordered array with long range order. In amorphous materials, they have only short range order. In amorphous materials, they are randomly distributed.
In Einstein's Theory of Gravitation, we understand the gravitational field
as a warping of space-time by a massive object.
According to Newton, when the distance between two interacting objects triples (distance is multiplied by 3), the gravitational force is
one ninth as much.
The density of a 5-cubic meter block of mass 1000 kg is
200 kg/m/m/m d=m/v
An isotope is simply an atom that
has different numbers of neutrons for the same element.
Which of these has the greatest number of protons in its nucleus? A) aluminum B) copper C) carbon D) gold
Gold
A solid block of copper is mostly empty space because the atoms in the block are
mostly empty space themselves.
Compared to the density of water, the density of a stationary fish in the middle of a pond is
the same.
In regards to atoms that make up ordinary matter, which of the following is not true? A) the lightest and most abundant atom is hydrogen B) atoms of an element can have different numbers of electrons C) atoms are in perpetual motion D) we know of more than 1000 distinct elements that make up ordinary matter
D) we know of more than 1000 distinct elements that make up ordinary matter
An object has the shape of a cube and is fully submersed in water. If the direction of gravity is downward, then best explanation of why the buoyant force acts upward on the submersed cube is because
the water pressure against the bottom of the cube is greater than the water pressure against its top.
The strength of a rope depends on its
cross-sectional area (thickness)
One thing that Tidal friction is causing
is the Earth to slow its rotational rate very, very gradually.
The discovery of the Higgs boson will likely
change our idea of what it means for matter to have mass.
Although solid matter is mostly empty space, we don't fall through the floor because of
electrical forces.
A creature that is scaled up in size, keeping its proportions,
will be weaker relative to its greater weight.
One side of the Moon continually facing Earth is
a tidal lock.
Surface tension of water is not responsible
for buoyancy.
When holes are drilled through the wall of a water tower, water will spurt out the greatest horizontal exit speed from the hole closest to
the bottom of the tower.
What is true about drinking water from a straw?
Air pressure pushes water up the straw, so straws can only be at most 10.3 m in height.
When the curve of a vertical structure matches the inverted image of a drooping chain held at both ends,
the curve is called a catenary.
As a fluid gains speed, its internal pressure
decreases.
The air of the atmosphere is best describes as
a mixture.
The mass of matter is due mostly to
its nucleons (protons and neutrons)
The cosmos is comprised mostly of
Dark Energy
What is the event horizon of a black hole?
Boundary where the forces of gravity about a collapsed star are so great that light cannot escape.
A mass is attached to a spring and the spring is set into simple harmonic oscillation. Where is the speed of the mass greatest?
At the equilibrium point where the mass hangs when not in oscillation.
Hooke's Law
is a principle of physics that states that the force needed to extend or compress a spring by some distance is proportional to the stress applied to it.
Boyle's Law
pressure and volume of a gas enclosed in a space are inversely proportional.