Physics - Chapter 4: Newton's Laws

Unit 3

Force

Change velocity, cause acceleration, start, stop, or change direction of motion

Equilibrium

Object at rest or moving w/ constant velocity w/ zero acceleration and zero net force; forces are balanced

Newton’s 1^st Law

Object at rest or in motion keeps constant velocity unless acted upon by a non-zero net force

Inertia

Objects tendency to resist motion; large mass = large inertia = less acceleration

Hard to change state of motion

Newton’s 2^nd Law

F_net=ma

Describe the relationship acceleration has between net force and mass

directly proportional to the net force (2 quantities move together)

inversely proportional to the mass (2 quantities move in opposite directions)

Newton’s 3^rd Law

For every action, there is an equal and opposite reaction

What’s an example of Newton’s 3^rd Law?

When swimming, you push the water backward, water pushes you forward with the same amount of force

Contact forces

needs physical contact between the object and its surroundings (N and F_f)

Field forces

acts on the disconnected objects (gravitational and electric forces)

Mass (m)

measures the amount of matter and remains constant

Weight (Fg)

measures the gravitational pull on an object with mass and it depends on the location Fg=mg

Compare f_s and f_k

• point in opposite directions

• directly proportional to N

• depends on the composition properties of the surface on which objects moving

Contrast f_s and f_k

• f_s prevents an object from moving

• f_k hinders the motion of the object

• f_s > f_k