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95 Cards in this Set

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An object weighs 30N on earth. A 2nd object weighs 30N on the moon.Which has the greater mass?
30-N on the moon
hypothesis
an educated guess
Which has more mass, a kg of feathers or a kg of nails
they are both the same
What approximates the best resultant of a pair of 10-unit vectors at right angles to each other?
14-units
work/time
power
a rock that is thrown straight up reaches the top of its path and is starting to fall back down. what is its acceleration?
9.8 m/s/s
force x distance
work
What is the resultant of a 4-unit and 3-unit vector at right angles to each other
5 ( think multiples when dealing with 3-4-5 triangles)
If you lift one load up 2 stories how much work do you do compared to lifting it up only one story?
2xs the work
What is the resultant of a 4-unit and 3-unit vector at right angles to each other
5 ( think multiples when dealing with 3-4-5 triangles)
the energy due to position
Potential energy
A rifle with a muzzle velocity of 100m/s is fired from a tower. Neglecting air resistence, where will the bullet be 1 s later?
100 m
A 10 N force and a 30 N foce act in the same direction. what is the net force?
40 N
Does the vertical velocity change the horizontal velocity?
no
how much does a kg of nails weigh?
9.8 N
give one unit of speed
k/h
The weight of a person can be represented by a vector that acts in what direction?
downward
What is the resultant of a 4-unit and 3-unit vector at right angles to each other
5 ( think multiples when dealing with 3-4-5 triangles)
If you push a object w/ 2xs the force and 2xs the distance, how much does work increase?
4xs
In the abscence of air resistance, an object falls at a constant what?
acceleration
unit of work
joules
A cannonball is fired at some angle into the air. In the 1st second it moves 10 meters horizontally. Assuming it doesn't hit the ground and air resistance is small, how far does it move in the next second?
10 m
What is the maximum resultant when adding a 3N force to a 8N force?
11N
speed
d/t
units of power
watts
Jose can jump vertically 1 m on his skateboard when it was at rest. How far can Jose jump?
1 m
If a woman stands on a scale w/ 2 feet and weighs 500-N, how much will she weigh if she lifts one foot?
500-N
when an object falls freely from acceleration, what increases?
its velocity
What is the minimum resultant possible when adding 3N and 8N?
5N
Does the vertical velocity change the horizontal velocity?
no
if you lift two loads up one story, how much work do you do compared to lifting one load up one story?
2xs the work
A ball tossed vertically upwards, reahes its highest point and then falls back to its starting point.During this time,the acceleration is always in what direction?
downward
1/2mv/v
kinetic energy
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 1st?
they both hit at the same time
An arrow in a bow has 70 J of PE.assuming no loss of energy due to heat, how much kinetic energy will it have after it has been shot?
70 J
what is a theory
it is observation that has not been proven wrong yet
How much farther will a car at 100 km/h skid than the same car at 50 km/h
4xs as much
If one object has twice as much mass as another object, then the object also has twice the __________.
momenum
what must an object with kinetic energy have?
momentum
An object tavels 2 meters in the 1st second of travel, 2 meters again in the 2nd second of travel and 2 meters in the 3rd second of travel. What is the acceleration
0
A woman can lift barrels a vertical distance of 1 m or can roll them up a 2 m long ramp at the same elevation. Which one will require 1/2 the force?
the 2m ramp
What is friction?
a force that acts as a force of touching objects
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 100 J of KE. Ignoring air friction, with how much kinetic energy does the second ball hit the ground?
100 J
Suppose an object is in free fall. Each second the object falls a ________ distance than the second before
farther
A job is done slowly and an identical job is done quickly. Both jobs require the same amounts of work but different amounts of what?
power
The mass of a dog that weighs 100 N weighs how much in kgs?
10
A ball is thrown into the air with 100 J of kinetic energy which is transformed to gravitational potential energy at the top of its trajectory. When it returns to its original level after encountering air resistance, what is its kinetic energy?
the same- 100J
when you look at the speedometer in a moving car, you can seethe car's ...
instanteous speed
Which requires more work: lifting a 50kg sack vertically 2m or lifting a 25kg sack up 4m vertically?
both require the same amount of work
Friction is a force that always acts in what direction?
the opposite direction
Energy is changed from one form to another with no loss or gain. What is this stament?
Always true.
physics is the most basic science because...
it is about the world around us
Which has a greater kinetic energy, a car traveling at 30 km/h or a half as massive car traveling at 60km/h?
60km/h
The force required to keep maintain an object at a constant speed in free space is equal to__.
0
If an object has linear kinetic energy then it must be what?
moving
Ten second after starting from resta car is movingat 40 m/h. What is the car's average acceleration?
4m/s/s
When bullets are fired from an airplane in the forward direction, what will happen to the momentum of the airplane?
it will decrease
You would have to travel to what planet to have the largest force if it only weighs 1-N on Earth?
Pluto
An object is dropped and falls freely to the ground with an acceleration of a 1 g. What is its acceleration if its thrown upward at angle?
still gravity - 9.8 m/s/s
Consider drops falling from a water faucet. When the drops fall they fall _________ than before
farther
At what part of the path does a projectile have minimum speed?
the top of its path
An object following a straight-line path at constant speed has__ _______ _______ __ __
no forces acting on it.
A projectile is fired horizontally in a vacuum. Whay does the projectile maintain its horizontal component speed?
because of Newton's 1st law
The hang time for most athletes are about?
less than one second
If a ball is thrown in the air at some angle. What will the ball's velocity be at the top of its path?
changing
If a an object weighs 10 kg on the earth then what does it weigh on the moon?
10 kg
A bullet fired horizontally hits the ground in 0.5 seconds. If it had been fired with a much greater speed in the same direction, it would have hit the ground when?(neglecting the earth's curvature and air restistance)
0.5 seconds
What is the average speed of a car going 100 kilometers in two hours
50 km/h
a car accelerates at 2 m/s/s. Assuming the car starts from rest., how much time does does it take to accelerate to s speed of 30m/s
15 s
If you push a car on the earth and as hard as you push it on the moon. why is this?
b/c of inertia
vector
a quantity that has magnititude and direction
What does the law of inertia apply to?
objects in motion or at rest
a horizontal component of a projectile is independent of the ....
vertical component
Equilibrium occurs when?
when the net forces equal 0
If you drop a faether and a coin at the same time in a vacuum tube, which will reach the bottom first?
both will fall at the same time
If the force of gravity suddenly stopped acting on the planets, what woul happen?
it continues in a straight line
A car accelerates at 5 m/s/s. Assuming the car starts from rest , how much time would it take to accelerate the car to 30 m/s/s?
6s
A 10-N force and a 30-N force act on an object in different directions. What is the net force of the object?
20-N
A ball is thrown sraight up its acceleration is what?
9.8 m/s b/c of velocity
A ball is thrown straight upward at 20m/s. Ideally, (no air resistance) the ball will return in the thrower's hand at what speed?
20m/s
what is a projectile?
a moving object
What does the law of inertia state?
it resists change to its state of motion (an object is lazy)
what are the components of a vector?
magnitude and d9irection
------->
A rifle with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, where will the bullet be in 10 seconds?
1000 m
Why will a ball never go as far as physics ideally predicts?
because of friction
If a ball rolls down one plane how far will it go up another?
to its initial point
scalar
quantity that has magnitude
How much force is needed to keep a cannon fired into frictionless space going?
0
If a free falling object were somehow equiped with a sppedometer, its speed would increase by __ m/s
9.8
A sheet of paper can be withdrawn from under a container if milk without toppling it if the paper is jerked quickly. Why can this be done?
because of inertia
Suppose a car is moving in a straight lineand steadily increases its speed. It moves from 35 km/h to 40 km/h and from 40 km/ h the next second. What is the acceleration?
5km/h
In the abscence of air fricton, does a vertical component of a projectile's velocity change as the projectile moves?
no, it does not
A ball is thrown straight up. Its instaneous speed at the top of its path is what?
0 (but its velocity is not)
At the instant a ball is thrown horizontally with a large force an identical ball is dropped from the same height. which the ball hits the ground first?
both fall at the same time
When there is no air resistance, a ball would go the farthest if thrown at this angle
45 degrees