Newton's Laws Flashcards
A hockey puck sliding across the ice finally comes to rest because
of friction
When no forces act on moving objects their paths are normally
straight lines
A vehicle undergoes acceleration when it
changes direction, loses speed, gains speed
Newton’s 1st law
inertia
Inertia
a tendency to do nothing or to remain unchanged.
If gravity between the Sun and Earth suddenly vanished, Earth would continue moving in
a straight-line path.
Which concept is being illustrated when a tablecloth is quickly yanked beneath dishes resting on a table?
inertia
Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the tendency of the rock is to
follow a straight-line path.
force
push or pull
uniform speed
constant speed
Acceleration
speeds up OR changes direction
normal force/support force
force that holds things up. opposite of gravity
speed
distance per time
velocity
displacement/time
displacement
how far an object is moved from one place to another. not distance traveled, distance away, think straight-line
vector
direction
magnitude
length of vector
instantaneous speed
speed measured at instant of measuring
Gravity’s force on Earth
10
Freefall
an object is in freefall is the only force acting on it is gravity
9.8 m/s2
the speed of acceleration of a fall
change in velocity over time
∆v /t
acceleration
Newton’s 2nd Law
f=ma
kinetic
in motion
static
at rest
m (mass) *g (gravity) =
w (weight)
Newtons
measures force and weight (weight is a force)
When a rocket ship gaining speed in outer space runs out of fuel, it
no longer gains speed.
A force is a vector quantity because it has both
magnitude and direction
Does a car’s odometer measure distance traveled or displacement?
distance traveled
While you are standing in the aisle of a bus, the driver suddenly makes a left turn. You lurch to the right due to
your tendency to keep moving forward
Does the speedometer of a car measure speed or velocity?
speed
Suppose you throw a rock straight upward. What is the acceleration of the rock while it is on the way up?
9.8 m/s2 downward
Suppose you throw a rock straight upward. What is the acceleration of the rock at the very top of its flight?
9.8 m/s2 downward
Suppose you throw a rock straight upward. What is the acceleration of the rock on the way down?
9.8 m/s2 downward
True or false: If you get a ticket for speeding, it is based on your average speed, not your instantaneous speed.
False
True or false: One bullet train travels due north at 220 km/h and another train travels due south at 220 km/h. These trains have the same speed.
True
True or false: One bullet train travels due north at 220 km/h and another train travels due south at 220 km/h. These trains have the same velocity.
False
Light travels in a straight line at a constant speed of 300,000 km/s. The acceleration of light is
0 km/s
True or false: As speed increases for an object in free fall, the acceleration increases as well.
False
While an object near the Earth’s surface is in free fall, its
velocity increases
An object at rest near the surface of a distant planet starts to fall freely. If the acceleration there is twice that of the Earth, its speed one second later would be
20 m/s
If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by about
10 m/s
A rock dropped from a 5-m height accelerates at 10 m/s2
and strikes the ground 1 s later. If the rock is dropped from a height of 2.5 m, its acceleration of fall is
the same
A cart changes its speed from 90 m/s to 100 m/s in 10 seconds. During this interval its acceleration is
1m/s2
A freely-falling watermelon falls with constant
acceleration
The time it takes a projectile fired straight up at 10 m/s to reach the top of its path is about
1 s
Whenever the net force on an object is zero, its acceleration
is zero
If an apple experiences a constant net force, it will have a constant
acceleration
A 10-N falling object encounters 10 N of air resistance. The net force on the object is
0 N
A 1-kg mass at the Earth’s surface weighs
10N
A pair of action-reaction forces always
comprise a pair of interactions
Two balls are thrown straight up into the air from the same location and with the same speed. One ball has twice the mass of the other. Neglecting air resistance, which ball will achieve the greatest height?
neither, they will achieve the same height
If a freely falling object were equipped with a speedometer on a planet where the acceleration due to gravity is 20 m/s2, then its speed reading would increase each second by ________
20 m/s
A mobile phone is pulled northward by a force of 10 N and at the same time pulled southward by another force of 15 N. The net force on the phone is __________
5N
A heavy truck crashes into a much lighter car. Which object receives the strongest force of impact?
the impact forces are equal in strength for both objects
The mass of a lamb that weighs about 110 N is about
11 kg
Compared to the mass of an apple on Earth, the mass of the apple on the moon is
the same
An apple at rest weighs 1 N. The net force on the apple when it is in freefall is
1 N
A car traveling on a straight road maintains a constant velocity of 40 m/s for 10 seconds
4 m/s2
A 2 kg mass at the Earth’s surface weighs
20 N
A box is being accelerated across perfectly frictionless ice by a 13N force. Suddenly the box encounters a second force of 13N in the opposite direction. With both forces acting on the box it
continues at the speed it had when it encountered the second force.
When a rocketship gaining speed in outer space runs out of fuel, it
no longer gains speed, remaining at a constant velocity.
The two measurements necessary for calculating average speed are
distance and time.
When you walk at an average speed of 4 m/s in 5 s you’ll cover a distance of
20 m
For an action force, there must be a reaction force
that is exactly equal in magnitude
Consider drops of water that leak at a steady rate from a dripping faucet. As the drops fall they
get farther apart
If one object has twice as much mass as another object, it also has twice as much
inertia
When a rock thrown straight upwards gets to the exact top of its path, its
velocity is zero and its acceleration is about 10 m/s2
The force of friction on a sliding object is 10N the applied force need to maintain a constant velocity is
10N
When you rub your hands together, you
cannot push harder on one hand than the other.
When you walk, you push on the floor to the left and the floor
pushes you to the right.
