A. 2 Forces & Mometum

What are Newton’s Three Laws of Motion in plain words?

First Law: An object stays still or moves at a steady speed in a straight line unless a total force acts on it.

Second Law: Total force equals the rate of change of momentum. If mass is constant, this is just Force equals mass times acceleration.

Third Law: If object A pushes object B, then object B pushes object A back with the exact same amount of force in the opposite direction.

What is a Free-Body Diagram and how is it used?

A drawing of one object showing all the outside forces hitting it as arrows. It is used to find the "resultant force," which is the single total force that determines how the object moves.

What is the Normal Force?

The part of a contact force that acts at a right angle (perpendicular) to a surface. It is the support force that stops an object from falling through a floor or table.

Describe Static and Dynamic Friction without symbols.

Static Friction: The force preventing an object from starting to move. It can grow up to a maximum limit (the coefficient of static friction times the normal force).

Dynamic Friction: The constant friction on an object that is already sliding. It equals the coefficient of dynamic friction times the normal force.

What is Tension?

A pulling force passed through a string, rope, or cable when it is pulled tight by forces at each end.

What is the rule for the Elastic Restoring Force (Hooke’s Law)?

The force pulling a spring back to its original shape equals the spring constant times the distance it was stretched. The force always pulls in the opposite direction of the stretch.

What is Stokes' Law for viscous drag in words?

The drag force on a tiny ball moving through a liquid equals six times pi times the thickness of the liquid times the radius of the ball times its speed.

What is Buoyancy?

An upward lifting force. It equals the density of the liquid times the volume of the liquid moved out of the way times the strength of gravity.

What are the three Field Forces?

Gravitational Force: Weight (mass times gravity).

Electric Force: Pushes or pulls between charges.

Magnetic Force: Forces caused by magnets or moving charges.

What is Linear Momentum and the law for it?

Momentum equals mass times velocity. The law says the total momentum stays exactly the same unless a total force from the outside acts on the system.

What is Impulse and how does it change momentum?

Impulse equals the average force times the amount of time that force was touching the object. The impulse given to an object is exactly equal to the change in that object's momentum.

How is Newton’s Second Law used when mass is changing?

Force equals the change in momentum divided by the change in time. This is more accurate than mass times acceleration for things like rockets that lose mass as they burn fuel.

What is the difference between Elastic and Inelastic collisions?

In both, momentum is saved. However, in an Elastic collision, the energy of motion (kinetic energy) is also saved. In an Inelastic collision, some of that energy is lost to heat or sound.

What is an Explosion in physics terms?

When one object breaks into many pieces moving away from each other. The total momentum of all the pieces added together must equal the momentum the object had before it exploded.

What is Centripetal Acceleration?

Acceleration that points directly toward the center of a circle. It equals the speed squared divided by the radius of the circle.

What is Centripetal Force and what is its job?

The "center-seeking" force needed to keep an object moving in a circle. It acts at a right angle to the object's movement, meaning it changes the object's direction but does not change its speed.

What is Angular Velocity?

A measure of how fast an object is turning through an angle. The regular speed along the edge of a circle equals the angular velocity times the radius.

What is Translational Equilibrium?

A state where the total resultant force on an object is zero, meaning the object is either perfectly still or moving at a constant velocity in a straight line.