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# Forces

## Terms

undefined, object
copy deck
What kind of force causes an object moving in a circular motion to accelerate towards the center of a circle?
centripetal force
What is a NET FORCE?
... the sum of all forces acting on an object.
What kind of forces always change the motion of an object?
... unbalanced forces.
What is an UNBALANCED FORCE?
... a nonzero net force that changes the motion of an object.
What is the centripetal force of acceleration that causes a car traveling around a bend in the road to follow a curved path?
friction
What is Newton's first law of motion?
An object at rest will remain at rest and an object in motion will remain in motion at a constant speed unless acted upon by an unbalanced force.
What unbalanced force causes objects to accelerate towards the Earth's surface at a rate of 9.8 m/s2?
... gravity.
What is a FORCE?
... a PUSH or a PULL.
What is a PROJECTILE?
An object that is thrown or tossed through the air.
What are BALANCED FORCES?
... forces that are EQUAL in magnitude (size) but OPPOSITE in direction.
What kind of forces never change the motion of an object?
... balanced forces.
What is INERTIA?
... the tendency of an object to resist a change in its motion.
What is MOMENTUM?
The property that an object has due to its mass and velocity.
What is Newton's second law of motion?
The net force on an object is the product of its mass and acceleration.
The symbol for Newton is _____.
N
What is the mathematical formula given by Newton's second law of motion?
Force = Mass x Acceleration
OR
F = m x a
What are the UNITS of MOMENTUM?
kg x m/s
What is the metric unit of measurement of force?
... Newton (N).
What force always acts opposite to the direction of motion of an object and acts to slow it down or cause it to stop moving?
... friction.
Newton's first law of motion is also called the law of __________.
... inertia
What two forces must be balanced in order for terminal velocity to be reached?
The downward force of WEIGHT due to gravity and the upward force of AIR RESISTANCE.
The amount of force required to accelerate a 1 kg mass at a rate of 1 m/s2 (meter per second squared)is a _________.
... Newton
What is the net force of forces that are equal in magnitude (size) but opposite in direction acting on an object?
... zero.
In terms of the metric units for mass and acceleration, what is a Newton equivalent to? (Hint: Think of Newton's second law only in units!)
N = kg x m/s2
What does it mean for an object to be in FREE FALL?
The only force acting on the object is gravity.
Which law of motion best explains the need to wear a helmet when riding a motorcycle?
Newton's third law of motion
What type of forces always result in a nonzero net force acting on an object?
...unbalanced forces.
What famous Italian scientist is credited for proving that all objects, regardless or their mass, will fall and accelerate at the same rate in the absence of air resistance or in a vacuum?
Galileo
What does the LAW OF CONSERVATION OF MOMENTUM state?
The total momentum of a group of objects remains the same unless acted upon by unbalanced outside forces.
What does Newton's third law of motion state?
For every action (force), there is an equal and opposite reaction (force).
What are four ways that an unbalanced force can change the motion of an object?
1.) Cause an object at rest to start moving, 2.) stop and object in motion from moving, 3.) change an object's speed, or 4.) change an object's direction.
How many laws of motion are there?
Three.
What is a SATELLITE?
An object that travels around another object in space.
As the mass of an object increases, what happens to the universal force of attraction due to gravity between it an another object?
The force of gravity increases.
What is the FORMULA for MOMENTUM?
p = m x v
What is the pair of forces referred to in Newton's third law of motion called?
An action - reaction pair.
What is the centripetal force that keeps a satellite in orbit?
Gravity
What law of motion best explains why you should wear a seatbelt when driving to ensure your safety?
Newton's first law of motion.
What is TERMINAL VELOCITY?
The maximum speed that an object reaches at it is falling toward Earth.
What is the formula given by Newton's second law of motion when it is solved for acceleration?
acceleration = force / mass

OR

a = F/m
According to the law of inertia, an object in motion will keep moving at __________ speed unless acted upon by an unbalanced force.
constant
As the distance between two objects increases, what happens to the size of the universal force of attraction due to gravity between them?
The force of gravity decreases.
According to Newton's second law of motion, if the mass of an object increases and the force exerted on it stays the same, what happens to the rate of acceleration?
Acceleration decreases.
What law states that the force of gravity acts between all objects in the universe?
The Universal Law of Gravitation.
What is WEIGHT?
... a force that measures the pull of gravity on an object with mass.

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