1. Unit 2 - Forces

2. In this unit, you will be able to:
Define and describe concepts related to force – i.e. types of forces
State and apply Newton’s three laws of motion
Analyze the mathematical relationship among net force, mass and acceleration
Define and describe concepts related to the force of friction and gravity
Analyze the gravitation force acting on an object on the Earth’s surface
Design and carry out experiments to identify how friction affects the motion of a sliding object
Pg. 53 Reflect on Your Learning

3. Forces in Nature
force is described as a push or pull on an object
forces are everywhere and act on almost anything
a force applied to an object will sometimes change the shape and/or motion of the object
force is a vector quantity - it has magnitude and direction
the symbol for force is 𝐹 and it’s unit is the Newton (N)
one Newton is the amount of force required to accelerate a one kilogram object at one metre per second. (1N = 1 kg•m/s2)

4. The Four Fundamental Forces
Gravitational force (weakest)
force of attraction between all objects in the universe
Electromagnetic force
force caused by electric charge
Strong nuclear force
holds protons and neutrons together in the nucleus
Weak nuclear force
responsible for the fact that some nuclei are radioactive

5. Common Forces
𝐹 𝑔 - force of gravity
𝐹 𝑁 - normal force – force perpendicular to the surface of objects in contact
𝐹 𝑓 - force of friction – force between objects in contact and parallel to contact surface
𝐹 𝑇 - tension – force exerted by string or ropes
𝐹 𝐴 - applied force – pushing

6. Draw compass point and suitable scale
Free Body Diagrams
A vector diagram showing all the forces acting simultaneously on an object is called a free body diagram.
Drawing F.B.D.’s:
Draw compass point and suitable scale
Sketch the object isolated from it’s surroundings
Locate the centre of the object
Draw all force vectors acting on the object (note: always from the centre)
i.e. FBD for a car travelling at constant speed
𝐹 𝑁
1 cm = 1 N
𝐹 𝑓
𝐹 𝐴
𝐹 𝑔

7. Draw F.B.D.’s for the following situations:
A car accelerating
A car slowing down
A car travelling at constant speed up a hill
FBD Simulator
2.1 Prac. #7,9
UC #1-4