Force and Newton's Laws Test Flashcards
State the law of universal gravitation.
The force of gravity acts between all objects in the universe.
What is weight?
Weight is the measure of the force of gravity on an object.
Why do scientists prefer to describe matter by its mass instead of its weight?
Weight can change with location but mass will stay constant. Mass is how much matter is in an object.
What are two factors that affect the strength of gravity?
Mass and distance
How does mass and distance affect the gravitational attraction between two objects?
The more mass an object has, the greater the strength of its gravitational force; the greater the distance between two objects, the weaker the gravitational forces between them.
List two things that contrasts balanced gravity against unbalanced gravity.
Net force equals zero, does not chance an object’s motion
List two things that contrasts unbalanced gravity against balanced gravity.
Net force does not equal zero, changes an object’s motion
Compare unbalanced and balanced gravity.
A push or pull, strength and direction
What is static friction? Give an example.
Static friction is the friction that acts on objects that are not moving. Because of static friction, you must use an unbalanced force to start the motion of a stationary object.
Example – trying to move a stalled car to the side of the road. The heavier the object, the more static friction it has.
What is sliding friction? Give an example.
Sliding friction occurs when two solid surfaces slide over each other. Sliding friction is caused by the microscopic roughness of all objects.
Example – throwing sand on an icy patch on the ground to help your footing
What is fluid friction? Give an example.
Fluid friction occurs when a solid object moves through a fluid (gas or liquid). This friction is much easier to overcome than sliding friction. Lubricants are used to help reduce sliding friction.
Example – water on a water slide, applying oil to a squeaky gate hinge
What is rolling friction?
Occurs when an object rolls across a surface. This friction is much easier to overcome than sliding friction. Rolling friction reduces the amount of contact between surfaces because of curved shape of a sphere/circle/
Example – wheels, ball bearings
How is a force described?
Strength and direction.
What is net force?
A combination of all forces acting on an object.
How can you find net force if two forces act in opposite directions?
You would subtract to find the net force.
Define Newton’s first law of motion.
An object at rest will stay at rest and an object moving at a constant velocity (motion) will continue to move at a constant velocity (motion), unless acted upon by an unbalanced force. This law is also called the Law of Inertia.
Define Newton’s second law of motion.
The acceleration of an object depends upon the object’s mass and the net force acting on the object.
acceleration = force/mass
Define Newton’s third law of motion.
For every action there is an equal and opposite reaction.
When an object speeds up, slows down, or changes direction, why is an unbalanced force involved?
If an unbalanced force was not involved then there would be no change in the object’s motion.
What are the SI units for acceleration, force, and mass?
acceleration = m/s² mass = kg force = N
What two factors affect the force of friction?
the types of surfaces involved
how hard the surfaces are pressed together
Identify one product of friction?
Heat, wear and tear, slows objects down
In what direction does friction act in regards to an object’s motion?
Friction acts opposite the direction of motion.
Thinking of Newton’s second law of motion, what are two ways to increase the acceleration of an object?
Decrease the mass of the object
Increase the force acting on the object
Define centripetal force.
Any force that causes an object to move in a circular path. A center seeking force.
How does gravity affect objects that are moving horizontally?
Gravity pulls objects that are moving horizontally toward the center of the Earth in the same way it pulls a dropped object.
Why can an object have a constant speed and still be accelerating.
The object could be changing directions.
Define inertia.
The tendency of an object to resist a change in its motion.
How is mass related to inertia? Give an example.
The greater the mass, the greater the inertia.
Example – An aquarium full of water versus an empty aquarium. The aquarium with water has more mass so it has more inertia. Therefore it is harder to move.
How does Newton’s first law explain what happens to passengers when a car stops quickly?
When a car stops quickly a person’s body wants to continue forward in a straight line even though the car is stopped. This is the result of a body’s inertia. If a person doesn’t wear a seat belt their head could hit the dash board or the windshield.
When a rocket is launched, are the forces acting on it balanced or unbalanced? How do you know?
When a rocket is launched, are the forces acting on it balanced or unbalanced? How do you know?
