Unit 3 - Forces

Question 1

Define force

Answer 1

Force: a push or a pull with a vector

Question 2

State all types of forces

Answer 2

F_g: present unless in a vacuum; always points to the ground

F_N: exerted by the surface the object is on; perpendicular to the surface (upwards)

F_a: results when another object makes contact with the main object; points toward push

F_T: results from pulling the object with a rope, string, etc.; points toward rope

F_f: the force that resists the motion of the object; always parallel to the surface and opposite of the F_a/F_T

Question 3

State all earthy forces

Answer 3

Gravitational Force: force of attraction between all objects

Electromagnetic Force: force caused by electrical charges

Strong Nuclear Force: force that holds protons and neutrons together in the nucleus of an atom

Weak Nuclear Force: force responsible for interactions involving elementary particles such as protons and neutrons

Question 4

Define Newton’s first law

Answer 4

• If no net force acts on an object, it maintains its state of rest or its constant speed in a straight line
• Unbalanced: when one force is greater than the other force (ex., trying to push a boulder)
• Inertia: the resistance an object has to a change in its state of motion
  
  • The more mass an object has, the more resistance to changes it has

Question 5

Define Newton’s second law

Answer 5

• The acceleration of an object is dependent upon two variables – the net force acting upon the object and the mass of the object
• The formula that represents this is F_net = mass x a
  
  • So, when F_net = 0, there is no acceleration on a given object; friction = applied force
• F_net is the external unbalanced forces acting on an object

Question 6

Define Newton’s third law

Answer 6

• For every action, there is an equal and opposite reaction.
• However, the forces can never be balanced because they act on different objects

Question 7

Define static friction

Answer 7

Static Friction: the force that prevents stationary objects from starting to move

Question 8

Define starting friction

Answer 8

Starting Friction: the amount of friction that is needed to get an object moving (maximum static friction) (the force that must be overcome to get an object moving)

Question 9

Define kinetic friction

Answer 9

Kinetic Friction: the friction involved when an object is moving along its surface

Question 10

Define coefficients

Answer 10

Coefficients: the ratio between the normal force and the frictional force: Ff/FN

Question 11

Three ways the applied force affects the normal force

Answer 11

• When an object is pushed horizontally, normal force = gravity
• When an object is pushed upwards, the normal force is assisted which decreases frictional force (less of the object touching the surface)
• When an object is pushed downwards, the normal force is increased which increases frictional force (more of the object to a greater extent)

Question 12

Define net work

Answer 12

Net work: work that causes acceleration

Question 13

Friction isn’t included in work, true or false

Answer 13

True

Question 14

Weight vs Mass:

Answer 14

Mass is a measurement of the amount of matter something contains, while Weight is the measurement of the pull of gravity on an object. Weight differs depending on gravity while mass remains constant.