How do forces affect the motion of an object?
A force can cause a resting object to move, or it can accelerate a moving object by changing the object's speed or direction.
What are the four main types of friction?
Static friction, sliding friction, rolling friction, and fluid friction.
How do gravity & air resistance affect a falling object
Earth's gravity acts downward toward the center of Earth. Gravity causes objects to accelerate downward, whereas air resistance acts in the direction opposite tothe motion and reduces acceleration.
In what direction does Earth's gravity act?
Earth's gravity acts downward toward the center of Earth.
Why does a projectile follow a curved path?
The combination of intitial forward velocity and downward vertical force of gravity cause of projectile to follow a curved path.
Force
A push or a pull that acts on an object.
Newton
the SI unit for force, equal to the force that causes a 1-kilogram mass to accelerate at a rate of 1 meter per second squared (1 N= 1 kg.m/s2
Net force
the overall force acting on an object after all the forces are combined.
friction
a force that opposes the motion of objects that touch as they move past each other.
Static friction
a friction force that acts on objects that are not moving.
Sliding friction
a friction force that opposes the motion of an object as it slides over a surface.
Rolling friction
a friction force that acts on rolling objects, caused by the change in shape at the point of rolling contact.
Fluid friction
a friction force that opposes the motion of an object through a fluid.
Air resistance
fluid friction acting on an object moving through the air.
Gravity
the attraction between any two objects because of their masses.
Terminal velocity
the constant velocity of a falling object when the force of the air resistance equals the force of gravity.
Projectile motion
the curved path of an object in free fall after it is given an initial forward velocity.
1st Law of Motion
according to Newton's first law of motion , the state of motion of an object does not change as long as the net force acting on the object is zero.
2nd Law of Motion
according to Newton's 2nd law of motion, the acceleration of an object is equal to the net force action on it divided by the object's mass.
example: acceleration=force over mass
Acceleration
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What is weight?
The force of gravity acting on an object. Example:
Weight= Mass X acceleration due to gravity.
Mass
the amount of matter in an object. A measure of the inertia of an object, which depends on the amount of matter the object contains.
Inertia
the tendecy of an object to resist a change in its motion.
sometimes called the 1st Law.
3rd Law of Motion
forces exist as equal and opposite force pairs.
Momentum
the product of an object's mass and its velocity.
example: momentum=mass X velocity
Momentum is conserved
in a closed system.
Law of conservation of momentum
law stating that the total momentum of a system does not change if no net force acts on the system.
Electric and magnetic forces
are the only forces that can both attract and repel.
Strong and weak nuclear forces
hold the nucleus together.
Universal Gravitation
states that every object in the universe attracts every other object.
Electromagnetic force
a force associated with charged particles, which has two aspects, electric force and magnetic force.
Centripetal force
a force that continously change the direction.
How is mass different from weight?
Mass is the amount of matter in an object, and weight is the force of gravity acting on an object.