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### Science now

Why do objects fall to the ground at the same rate? gravity
why does a heavier object fall with the same acceleration as a lighter object? Bc heavier objects have a greater gravitational force
What is the rate at which velocity changes over time? acceleration
at what rate do all objects accelerate towards earth? 9.8 m/s2
Equation for velocity Velocity=Gravity x time (v=gt)
what is the force that opposes the motion of objects through air? air resistance
what three factors affect the amount of air resistance acting on an object? size, speed, shape
what has a falling object that stops accelerating reached? its terminal velocity
why can free fall occur only where there is no air? bc without air, there's no air resistance
what are the two places that have no air resistance in space, in a vacuum
what is centripal force? the unbalanced force that causes objects to move in a circular path
what is everything on earth pulled towards the center by? gravity
compared to a falling object, is the downward acceleration of a thrown object faster or slower? slower
Newton's First Law Of Motion: 1) Obejcts won't move unless a force is put on it 2) objects with move at a constant speed until a force is put on them
according to Newton's first law, what will happen to the motion of objects with a certain velocity unless an unbalanced force acts on them? they will move constantly
if you were in a bumber car that stops when it hits another car, would you continue to move forward? why or why not? yes until the seatbelt stops you because of Newton's first law
what unbalanced force acts to stop a desk that is sliding across a floor friction
what does friction do to the motion of objects? slow them down
what is the tendancy of an object to resist being moved until an outside force acts on the object? inertia
why is it easier to change the motion of an object with a small mass? because it has more inertia
Newton's Second Law of Motion: the acceleration of an object depends on the mass of the object the amount of force applied
what happens to the acceleration of an object as its mass decreases? acceleration increases
what happens to the acceleration of an object if the force on the object increases? acceleration increases
why would a cart start moving faster if you gave it a hard push than if you gave it a soft push? because i'm putting more force on it
Equation for Acceleration: Acceleration=Force/mass (a=f/m) Force= mass x acceleration (f=am)
why is an apple easier to accelerate than a watermelon it has less mass
Newton's Third Law: Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force
what action and reaction forces are present when you are sitting on a chair your weight pushing down on the chair; the chair pushing up on your body
why does it take a large truck longer to stop htan a compact car, even though both are traveling at the same velocity? because the truck has more weight
why does a fast moving car have more momentum than a slow-moving car of the same mass? it has a greater velocity
Equation for Momentum: Momentum=mass x velocity (p=mv)
if a cue ball hits a billiard ball so that the billiard ball starts moving and the cue ball stops, when happens to the cue ball's momentum? All of the cue ball's momentum has been transferred to the billiard ball.
how do action and reaction forces move a swimmer forward in the water? swimmer's hand pushing on the water; the water pushing back up on the hand
when a ball falls to earth, why is it hard to see the effect of the reaction force exerted by the ball on Earth? the acceleration of the Earth is so small that you can't see or feel the acceleration
what is one way that you can tell that the bowler has done work? the ball has kinetic energy
what has the bowler transferred to the ball when the ball has kinetic energy? energy
what two things need to happen for work to be done on an object? 1) the object moves as a force is applied 2)object must move in the same direction as the force
Equation for Work: Work= Force x Distance (W=Fd)
What is the rate at which work is done or energy is transformed? power
Equation for power: Power= Work/time (P=W/t)
what is a device that makes work easier by changing the size or direction of force? a machine
what type of common machine is a screwdriver that is used to pry off the lid on a paint can? a lever
what is the work you do on an object called? work input
what is the work done by a machine on an object called? work output
what can work output never be greater than? work input
why do machines need less force to do the same amount of work? machines allow force to be applied over a greater distance
when a screwdriver is used to open a can, both the size and what change? input force
a ramp will decrease the size of the input force needed to life a box and does what to the distance over which the force is exerted? increases it
what is the number of times a machine multiplies force called? mechanical advantage
What is the quantity that measures the ratio of work output to work input called? Mechanical efficiency
Equation for Mechanical efficiency: Mechanical Efficiency=work output/work input x100
when a machine drills a hole in metal, some of the work input is used to overcome what betweent the metal and the drill? friction
what would a machine that had 100% efficiency be called? an ideal machine
what do some machines use to lower friction between moving parts? lubricants
what is the ability to do work called? energy
work is a transfer of what? energy
what is the energy of motion? kinetic energy
in the formula for kinetic energy, what does the "m" stand for? mass
how does increasin mass affect kinetic energy? the greater the mass, the greater the kinetic energy
when you lift an object, energy is transferred to the object which gives the object what? gravitational potential energy
the amount of gravitational potential energy that an object has depends on what two things? weight and height above surface
Equation for gravitational potential energy: gravitational potential energy=weight x height
what is the amount of force that must be used on an object to lift it? weight
Equation for Kinetic Energy: Kinetic Energy= (mass x velocity2)/2 (KE= mv2/2)
Law of Universal Gravitation part 1: Gravitational force increases as mass increases
Law of Universal Gravitation part 2: Gravitational force decreases as distance increases

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