Some Particular Forces Weight = mg (direction: downward) mass 9.8 m/s2 Free body diagram: mg Mass and weight are not the same thing! Mass is an intrinsic property of an object Weight depends on the value of gravity

The Support()Force Fs= support force S F = 0, since at rest mg Any object in contact with a surface experiences a support force (Fs) perpendicular to that surface In the picture above: Fs = mg But this is not always the case!…….

Solve Unknowns Determine the magnitude of the forces acting on the 2 kg masses at rest below. ∑Fx = 0 and ∑Fy = 0 mg = 20 N FN = 20 N Solve Unknowns ∑Fy = 0 FN - mg = 0 FN = mg = 20 N

Examine the following diagrams and write 2-3 facts and figures about them…

Tension (T) – force applied by a string or rope Ex: 5 N T = 5 N We say “the tension in the string is 5 N” The tension is the same throughout a string, even when it passes over pulleys: T

Ex: A person pulls a crate across the ice with a rope Find the horizontal acceleration of the crate. 15 N m=35 kg 30

Static friction (fs) – keeps objects from moving Friction (f) – a force that opposes motion between two surfaces in contact motion (or attempted motion) friction Two types of friction: Static friction (fs) – keeps objects from moving Kinetic friction (fk) – opposes motion while moving Both depend on: Surfaces in contact Amount of normal force (FN)

Heat energy is always produced. Friction is a force. It occurs when two surfaces rub together. Heat energy is always produced.

Friction always opposes motion. Drag Thrust

Streamlining objects can reduce this effect.

1. Identify different types of forces, and describe how forces are measured. support drag thrust weight

1. Identify different types of forces, and describe how forces are measured. drag thrust weight support support friction friction Extension

1. Identify different types of forces, and describe how forces are measured. upthrust drag thrust weight

1. Identify different types of forces, and describe how forces are measured. drag upthrust thrust weight Extension

1. Identify different types of forces, and describe how forces are measured. upthrust drag thrust weight

1. Identify different types of forces, and describe how forces are measured. upthrust drag upthrust drag weight thrust Extension

AP Physics 1 G11! Fs mg sin(q) mg cos(q) q Force Components ~ Frictionless incline y x Fs AP Physics 1 G11! mg sin(q) mg cos(q) mg q q

Draw arrows to link these correctly. Some may be used more than once. Pushes and Pulls Draw arrows to link these correctly. Some may be used more than once. ... measured in kilograms ... how much material you’re made of ... the same on the Earth and on the Moon ... how hard the Earth pulls on you ... about 10 N/kg ... won’t return to its original length ... measured in newtons ... less on the Moon than on Earth The Earth’s surface gravity is... Your mass is... A spring stretched beyond its elastic limit ... Your weight is...

Answers Pushes and Pulls The Earth’s surface gravity is... Draw arrows to link these correctly. Some may be used more than once. ... measured in kilograms ... how much material you’re made of ... the same on the Earth and on the Moon ... how hard the Earth pulls on you ... about 10 N/kg ... won’t return to its original length ... measured in newtons ... less on the Moon than on Earth The Earth’s surface gravity is... Your mass is... A spring stretched beyond its elastic limit ... Your weight is...