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KNSS 201: Biomechanics > Linear Kinetics (Forces) > Flashcards

Linear Kinetics (Forces) Flashcards

1
Q

What is Newton’s 1st law?

A

an object at rest or moving at a constant velocity at a straight line will stay that way unless acted upon by a external force

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2
Q

What is Newton’s 2nd law?

A

The acceleration of a body is proportional to, and takes place in the direction in which the force acts. It is also inversely proportional to the body’s mass
F = ma

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3
Q

What is Newton’s 3rd law?

A
  • for every action there is an equal and opposite reaction
  • for every force that is exerted by one body on another, there is an equal opposite force exerted by the second body on the first
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4
Q

What is friction?

A
  • force that resists the sliding of 2 objects in contact
  • vector quantity
  • opposite of sliding potential
  • parallel to surfaces in contact
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5
Q

What is normal force?

A
  • vertical component (gravity) acts downwards

- ground reaction (normal) force acts upwards

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6
Q

What is friction force?

A
  • horizontal component: acts parallel to surface

- opposite to applied force (and to potential sliding direction)

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7
Q

What is static friction?

A

2 surfaces are not sliding, but have the potential for movement

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8
Q

What are the 3 factors that affect static friction?

A
  • texture of surfaces
  • weight of block
  • applied force
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9
Q

As friction increases, motive force needs to _____.

A

Increase

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10
Q

What is the coefficient of friction (μ)?

A
  • the proportion of friction force resisting the sliding motion of the object to the normal force holding the objects together
  • a constant for any 2 surfaces
  • how difficult it is to move a given surface over another surface
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11
Q

How does texture affect static friction?

A
  • grooves, scratches, and pores interlock/interact with texture on the other surface and impede motion
  • the more interactions between the 2 surfaces, the higher the value of μ
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12
Q

What is the value of μ for a totally frictionless interaction?

A

0.00

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13
Q

What is kinetic friction?

A
  • sliding surfaces

- grooves/pores “bumping”

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14
Q

What is rolling friction?

A
  • occurs when 1 surface is rolling over another
  • ## still depends on coefficient of friction and normal force
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15
Q

Coefficient of rolling friction is much ____ (less/more) than that of static of kinetic friction.

A

less

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16
Q

Rolling friction is actually a specialized case of ____ friction.

A
  • static

- trying to avoid sliding, want to maintain static friction

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17
Q

What is the general term for a force that is perpendicular to friction?

A

Normal force

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18
Q

What are the 3 types of friction?

A
  • static
  • kinetic
  • rolling
19
Q

What is momentum?

A
  • momentum of a body is a product of its mass and velocity
  • momentum = mv
  • vector quantity
20
Q

What are the units for momentum?

A

kg m/s or Ns

21
Q

What is the conservation of momentum?

A
  • The total momentum of any given system will remain constant in the absence of any external forces
  • the momentum prior to an action is the same as the momentum following the action
22
Q

What is impulse?

A
  • constant force (F) x time (t) is called the impulse of the force
  • the impulse of a force is equal to the change in momentum which it produces
  • relates to Newton’s second law
23
Q

The best shock absorption technique is (relating to impulse):

A

decrease force over increased time (landings)

24
Q

The best way for abrupt change of direction is (relating to impulse):

A

increase force over decreased time

25
Q

The longer the time or larger the applied force, the ______ the change in velocity of body receiving force (duration of force application).

A

greater

26
Q

Energy transfers are not 100% efficient. Where does this loss of kinetic energy (energy due to motion) go?

A
  • sound
  • heat
  • absorption by deformation of the bodies involved
27
Q

What are elastic collisions?

A

bodies involved separate after collision

28
Q

What happens in a perfectly elastic collision?

A

momentum and kinetic energy is conserved

29
Q

What are inelastic collisions?

A
  • at least one body deforms

- bodies involved do not separate

30
Q

What is elasticity?

A

the tendency of an object to return to its original shape once it has been deformed

31
Q

What are the 2 classifications of elasticity?

A
  • elastic impacts

- inelastic impacts

32
Q

What is the degree of elasticity?

A

coefficient of restitution (e)

33
Q

e is determined by…

A
  • composition of the object
  • composition of the surface of the object
  • temperature
34
Q

The value of e ranges from…

A

0 (inelastic) to 1.0 (perfectly elastic)

35
Q

What are the 2 types of impacts to consider?

A
  • direct

- indirect

36
Q

What are direct impacts?

A

when objects collide head on

37
Q

What are indirect impacts?

A

when objects collide at an angle

38
Q

_____ impacts are the ones we most commonly encounter in sports.

A

indirect

39
Q

For indirect impacts, the most important relationship to consider is that between the ______of ______ and ________. It is always measured from the _____.

A
  • angles of incidence and reflection

- perpendicular

40
Q

The angle of reflection depends on:

A
  • the elasticity of the object
  • the level of friction at the contact point
  • the amount of spin on the object
41
Q

What happens during direct contact?

A

outcome is usually spectacular and the deformation involves one or all of the colliding bodies

42
Q

Define pressure.

A

force (F) distributed over a given area (A)

43
Q

What are the units for pressure?

A

N per square m^2 or Pascals (Pa)

44
Q

How should you decrease pressure for landing pads?

A

increase area

KNSS 201: Biomechanics (7 decks)

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