Lecture 8 - Visualizing Forces

Question 1

what is a force?

Answer 1

• an action that causes mass to be accelerated

Question 2

what are Isaac Newton’s 3 Laws?

Answer 2

1. objects don’t want to be accelerated because they possess inertia
2. the force required to accelerate an object is proportional to it’s mass (F = m x a)
3. if a force is applied to an object, the object pushes back with the same force

Question 3

what is the law of inertia?

Answer 3

• mass doesn’t want to be accelerated
• if staying still wants to remain still
• if moving, wants to remain moving at that speed

Question 4

what is the law of force?

Answer 4

• m is a scalar
• acceleration and force go in the same direction
• amount of force needed can be determined by acceleration x mass

Question 5

what is the law of action/reaction?

Answer 5

• amount of force put into an object is returned (proportional)
• heavy objects return more force (painful)
• light object return less force (which is why they move)
• the ball doesn’t care what the foot is doing and vice versa (force acts on different objects which causes movement)

Question 6

what is the property of mass?

Answer 6

• magnitude (measured in kg)
• only 1 because scalar
• amount of matter that makes up an object

Question 7

what is the difference between mass and weight?

Answer 7

• mass is scalar, weight is a force (because of gravity)
• astronauts have the same mass in space but their weight is different

Question 8

what are the properties of weight?

Answer 8

• a force (gravity)
• measured in newtons (N) or lbs

Question 9

what are the 4 properties of a force?

Answer 9

• force is a vector
  1. has a magnitude
  2. has a direction
  3. has a point of application (where force is being applied)
  4. has a line of action (where force has been and where it is going)

Question 10

what is the center of mass?

Answer 10

• point of application of gravity
• aka center of gravity
• doesn’t have to be within the object
• can move around as body moves and weight is redistributed

Question 11

when might it be useful to put the center of mass outside of the body?

Answer 11

• lower center of mass = less force required
• for example: with high jump (fosbury flop)

Question 12

what are the components of force?

Answer 12

• resultant force = the line of force an object has (made up of horizontal and downward forces)
• angle of push = angle between horizontal and downward force you are pushing at (Pythagorean theorem)

Question 13

what are non-orthogonal forces?

Answer 13

• means the input forces are not at 90 degrees from each other
• us F1 and F2 (instead of horizontal and downwards)

Question 14

what is collinear force?

Answer 14

• all lines of action are parallel
• moving straight up while holding a weight for example

Question 15

what are the steps to draw a resultant force graphically?

Answer 15

1. draw the line of push (from POA)
2. draw a horizontal direction (from POA)
3. draw a vertical direction (from POA)
4. complete the rectangle