Physics Unit 2: Newton's Laws and Equilibrium (Khan Academy)

Planets revolve around the sun is an example of what?

It is an example of the first law of inertia where the planets keep revolving and never come to a stop.

Mass vs. Weight

Mass is a measurement of the amount of matter something contains, while Weight is the measurement of the pull of gravity on an object's mass. Weight is a FORCE.

Torque Clockwise

Negative

Torque

A force that causes rotation around the center of mass. (pivot point)

Law of Inertia

A law formulated by Galileo that states that motion, not rest, is the natural state of an object, and that an object continues in motion forever unless stopped by some external force.

Acceleration is proportional to the net force applied.

Acceleration is proportional to the net force applied.

Newton Firs Law of Motion (Law of Inertia)

An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity (ZERO ACCELERATION), unless acted upon by an unbalanced force. (Either positive acceleration or negative acceleration).

Example of Third Law of Motion

Exerting force on the ground by expelling gas particles. An astronaut throwing a big object to propel himself.

True or False: An unbalanced force on an object will always change the object's direction.

False, a counter example for this would be constant acceleration acting on a car in the positive direction.

True or False: An unbalanced force on a body will always impact the objects speed

False, speed is a scalar and it measures distance over time rather than displacement over time. Direction is not taken into account. Example, looking at an ice skater grabbing onto a rope while skating suddenly from above (inducing centripetal force), we will notice that theres a no change in displacement because he'd be going in circles which means we changed his velocity but his speed stayed the same. Earth rotating around the sun is another example.

True or False: an object in motion will slow down unless it is acted on by an unbalanced force.

False. an object in motion will be in motion unless acted upon by an unbalanced force. It can stay in motion there is a set of balanced forces or no forces at all.

Newton's Third Law of Motion

For every action there is an equal and opposite reaction

If an object is uniform, then the center of mass is going to be in the center (geometric center)

If an object is uniform, then the center of mass is going to be in the center (geometric center). If force applied to the center of mass, the whole object will move where the direction of the force is.

Force Unit

Newtons = kg·m/s²

Torque equation

T=Frsin(theta) [T=Fd] r=length of the lever arm F=magnitude of the force Ѳ= angel between the lever arm and force vectors

Newton's Second Law of Motion

The acceleration of an object is equal to the net force acting on the object divided by the object's mass. F=m*a Acceleration is proportional to the net force applied.

Center of Mass

The point in an object that moves as if all the object's mass were concentrated at that point

Why do gymnasts arch their back?

To bring their center of mass below the bar so they exert less force.

True or False: an object acted on by an unbalanced force will always accelerate the direction of the unbalanced force.

True

True or False: an object in motion will maintain its speed and direction forever unless acted on by an unbalanced force.

True

True or False: The reason why initially moving objects tend to come to rest in our everyday life is because they're are being acted on by unbalanced forces

True, example is friction, air resistance, gravity.

True or False: if the net force on a body is zero, its velocity will not change

True, if there are no forces acting on an object, it will have constant velocity. First law of motion.

True or False: an object at rest and an object in a constant velocity without any unbalanced force will behave and feel the same.

True. Law of inertia

True or False: an object at rest will stay at rest unless acted on by an unbalanced force.

True. No forces or balanced forces

Torque vs Work

Work is translational but torque is rotational. they do have the same unit.