physics semester 1
if an object is in true free fall how many forces are acting on it
1
a piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. after the putty sticks to the ball, both move with a combined momentum of
1 unit
a 1kg chunk of putty moving at 1m/s collides with and sticks to a 5kg bowling ball that is initially at rest. the bowling ball and putty are then in motion with a speed of
1/6m/s
if you exert a horizontal 100N force on a crate and it slides along a factory floor at constant speed then frictio between the crate and floor is
100N
a 10N book is at rest on a flat table. how many newtons os support force does the table provide
10N
if a squirrel drops out of a tree what is its speed when it hits someone's head
10m/s
drop a rock from a 5 meter height and it accelerates at 10m/s*2 for the first second. if the same rock is dropped from a height of 20 meters what is its acceleration rate (ignore air friction)
10m/s*2
if a rocket initially at rest accelerates at a rate of 40m/s*2 for 30 seconds its speed will be
1200m/s
a 4kg ball has a momentum of 48kg m/s. what is the ball's speed
12m/s
An object falls freely from rest on a planet where the acceleration due to gravity is 20m/s*2. in the first 4 seconds, it falls a distance of what
160m
two force vectors have magnitudes of 6N and 10N. what is the maximum possible sum of the two
16N
a 6kg fish swimming at a speed of 1m/s swallows an absent-minded 1kg fish swimming toward it at 4m/s. the speed of the larger fish after lunch is
2/7m/s
a 1000kg car moving at 10m/s brakes to a stop in 5s the average breaking force is
2000N
in the diagram at the right, Burl has moved toward the left end of the staging. what does the right scale now read
200N
It takes 3 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft?
45m
ignoring friction if an object is dropped on a planet where the acceleration due to gravity is 9m/s*2 what will its speed be in 5 seconds
45m/s
in the absence of air frictions if you throw an object downward at a speed of 20m/s its acceleration after being released will be what
9.8m/s*2
in mathematical notation the equilibrium rule is what
EF=0
Compared to a 1-kg block of solid iron, a 2-kg block of solid iron has twice as much
Inertia
What happens to an objects acceleration if the net force remains constant, but the mass is doubled?
It is decreased by half
What happens to an objects acceleration if the net force on it is doubled?
It is doubled
The kilogram is the measure of what?
Mass
Object "A" has a mass of 20 kg. Object "B" has a mass of 10 kg. Which object has the greater gravitational acceleration?
Neither
Which of the following is a unit of force?
Newtons
Which of the following is a unit of weight?
Newtons
Are mass and weight the same thing?
No
which of the following has the smallest momentum relative to the earth's surface
a large truck parked in the parking lot
which of the following has the largest momentum relative to the earth's surface
a mazda miata speeding along a highway
When you jump from an elevated position you usually bend your knees upon reaching the ground, which makes the time of the contact about 10 times that of a stiff-legged landing. In this way the average force your body experiences is
about 1/10 as great
a package falls off a truck that is moving at 30m/s. neglecting air resistence, the horizontal speed of the package just before it hits the ground is what
about 30m/s
Disregarding air resistance, objects fall with constant
acceleration
the "student killer" spins in a circular path over mr peer's head at a constant speed. what is true
acceleration is constant
what are examples of vector quantaties
acceleration velocity force
a karate expert executes a swift blow and severs a cement block with her bare hand the magnitude is the same for the
all of these
galileo used balls rolling on inclines to demonstrate what
an object at rest will remain at rest until acted on by an outside force
newtons first law states in part that
an object at rest will remain at rest until acted on by an outside force
how many forces are acting on the book at rest on the table
at least two forces
the bus speeds up while you are tossing your keys straight up, where do they land
behind your hand
You're driving down the highway and a bug spatters into your windshield. Which undergoes the greater change in momentum
both the same
which would be more damaging, driving into a very massive concrete call with no give or having a head on collision at the same speed with an identical car moving toward you with the same speed? it would be more damaging to hit
both the same
It is correct to say that impulse is equal to
change in momentum
if an object falls with constant acceleration the velocity of the object must
continuously increase
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 at all times what
directed downward
true or false? inertia is a force which keeps objects in a state of motion or in a state of rest
false
a rifle recoils from firing a bullet. the speed of the rifle's recoil is small b/c the
force against the rifle is smaller than against the bullet
what is impulse equal to
force times time
mr peer pushes a book across a level table at a constant speed in a striaght line. ignoring air friction, how many forces are acting on the book
four
A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time. Compared with the force that stops the car, the force needed to stop the truck is
greater
you toss your keys straight up while riding a bus along a straight line at a constant speed. where do the keys land
in your hand
Padded dashboards in cars are safer in an accident than non-padded ones because an occupant hitting the dash has
increased time of impact and decreased impact force
as mr peer carries a small sand bag across the room, what keeps it moving in a straight line at a constant speed
inertia
what keeps a space probe going after the rocket no longer pushes it
inertia
it is said that "the early bird catches the worm." if Copernicus was correct, how is it that the early bird in the tree can catch the worm on the ground
inertia makes it easy
what is a vector quantity
it has both magnitude and direction
Compared to the weight of a certain object on earth, the weight of the same object on the moon is
less
When you are in the way of a fast-moving object and can't get out of its way, you will suffer a smaller force of impact if you decrease its momentum over a
long time
compared to falling on a wooden floor, a light bulb may not break when it falls to a carpeted floor b/c of the
longer time to stop
A Force is a vector quantity because it has both
magnitude and direction
what is momentum equal to
mass times velocity
Two objects, A and B, have the same size and shape, but A is twice as heavy as B. When they are dropped simultaneously from a tower, they reach the ground at the same time, but A has a greater
momentum
a heavy object and a light object are dropped at the same time from rest in the world's largest vacuum chamber. which one hits the floor first
neither they hit at the same time
the conservation os momentum is most closely related to
newton's 3rd law
is it possible for an object to change speed while velocity remains constant
no
is it possible for an object to maintain constant velocity while accelerating
no
on a cold winter day mr peer slips on the ice and slides down the sidewalk constantly increasing speed. faster and faster he goes until the signpost at the bottom of the sidewalk brings his adventure to a sudden halt. prior to hitting the signpost, is he in mechanical equilibrium
no
a 1N apple falls to the ground. the apple hits the ground with an impact force of about
not enough information given to say
according to aristotle the normal state of an object on earth is a state of what
rest
galileo's use of inclined planes allowed him to effectively do what
slow down the acceleration of free fall
Your weight is
the gravitational attraction between you and the earth
a bullet is fired from a gun. the speed of the bullet would be about the same as the speed of the recoiling gun if
the mass of the bullet equals the mass of the gun
An object weighs 30 N on Earth. A second object weighs 30 N on the moon. Which has the smaller mass?
the one on earth
a ball is thrown upwards and caught when it comes back down. neglecting air resistance, its speed when caught is what
the same as the speed it had when thrown upward
Suppose a gun were made of a strong but very light material. Suppose also that the pellet is more massive than the gun itself. For such a weapon
the target would be safer than the shooter
ignoring air friction, if two pizzas, a small personal pan pizza and a large deep dish pizza, are dropped simultaneously from the leaning tower of pizza, which one will hit the ground first
they will hit at the same time
in order 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 upon impact. doing this reduces the force of impact on the player's hand because the
time of impact is increased
when talking about the parked miata, in what direction does the support force vector point
up
When a rock thrown straight upwards gets to the exact top of its path, its
velocity is zero and its acceleration is about 10m/s*2
a bowling ball rolls down the alley in a straight line at constant speed. is the ball in a state of equilibrium
yes
is it possible for an object to accelerate while maintaining a constant speed
yes
is it possible for an object to have zero velocity while accelerating
yes
is the book being pushed across a level table at a constant speed in a straight line in mechanical equilibrium
yes
Recoil is noticeable if you throw a heavy ball while standing on roller skates. If instead you go through the motions of throwing the ball but hold onto it, your net recoil will be
zero
if a boat can be paddled through still water at 4mph how fast will it travel if paddles upstream while the river is flowing at a speed of 3mph
1mph
a car accelerates from rest at 4 meters per second per second. what is its speed 5 seconds after the car starts moving
20m/s
if an object initially at rest accelerates at a rate of 6m/s*2 for 5 seconds, what will its speed be
30m/s
in the diagram at the right, Burl is standing exactly in the middle of the staging. the left scale reads 400N. what does the right scale read
400N
in the diagram at the right, Ed weighs 600N, the reading on the left scale is 700N, and the reading on the right is 300N. what is the weight of the staging
400N
two force vectors have magnitudes of 6N and 10N. what is the smallest pssible sum of the two
4N
mr peer's miata, which weighs about 2000 pounds is parked in the teacher's parking area, about how much support force is one each wheel
500 pounds
a ball is moving at 4m/s and has no momentum of 20m/s. what is the ball's mass
5kg
a squirrel drops out of the top of a tree and lands on mr peer's head in one second. how tall was the tree
5m
if a ball is tossed upward with a velocity of 30m/s how long will it be in the air before returning to its starting point
6 seconds
a 6kg fish swimming at a speed of 1m/s swallows an absent minded 1kg fish at rest. the speed of a larger fish after lunch is
6/7m/s
if a car increases its velocity from 10km/h to 70km/h in 10 seconds, what is its acceleration
6km/h/s
a car accelerates from rest for 5 seconds and reaches a speed of 30m/s. what is the car's acceleration in m/s*2
6m/s*2
if an object initially at rest accelerates at a rate of 6m/s*2 for 5 seconds what distance does it travel
75m
copernicus was known for what theory
the earth circles the sun
the net force on any object in equilibrium is what
zero
what is the net force on the book described on a book that is at rest
zero