Exam 2: mass/force-forces dependent on other variables

Question 1

Kinetics

Answer 1

combines kinematics with causes of motions

Question 2

what 2 quantities does kinematics require?

Answer 2

1. mass
2. force

Question 3

mass

Answer 3

a measure of objects resistance to acceleration
- how hard it is to accelerate an object

Question 4

large objects have _____ acceleration; small objects have ______ acceleration

Answer 4

small; big

Question 5

SI units of mass

Answer 5

kg

Question 6

mass is a ________ _______ not ______

Answer 6

positive number; directional

Question 7

when you multiply mass by a vector what happens to direction?

Answer 7

it is unchanged

Question 8

force

Answer 8

a vector that measures intensity and direction of pushing or pulling on an object

Question 9

SI units of force

Answer 9

kg(m)/time^2 - Newtons (N)

Question 10

2 ways that forces occur

Answer 10

1. weight
2. contact with another object

Question 11

weight definition

Answer 11

force applied to an object by gravity
- not equal to mass
- mass in mg (9.8 m/s^2) down always

Question 12

3 main force types

Answer 12

1. weight
2. pushing
3. pulling (cables)

Question 13

what do FBDs consist of?

Answer 13

object(s) + forces only

Question 14

pushing

Answer 14

perpendicular direction to surface of contact toward chosen body

Question 15

T/F when two bodies push on one another they have the same pushing force?

Answer 15

True

Question 16

pulling (cables)

Answer 16

parallel to the cable and away from the body

Question 17

T/F when two bodies are connected by the cable, tension is not the same

Answer 17

False, tension is the same on each body

Question 18

Newtowns 2nd law eq

Answer 18

F(vector) net = m(a vector)

Question 19

Newtons second law definition

Answer 19

sum of forces acting on an object equals the mass of the object times the acceleration of the object

Question 20

what do you use when forces are not parallel or perpendicular along a line of motion?

Answer 20

use a right triangle to find the component of force along the line of motion

Question 21

what does it mean if force is <90 degrees from the positive direction?

Answer 21

the force component is +

Question 22

what does it mean if force is >90 degrees from the positive direction?

Answer 22

the force component is -

Question 23

3 cases of forces dependent on other variables

Answer 23

1. time dependent forces
2. spring (position dependent)
3. medical application: muscle models using the Stanford model

Question 24

forces as functions of time should use _____ in _____ if taking derivatives/integrals of ______ functions

Answer 24

angles; radians; trigonometric

Question 25

what does it mean if a force function gives a negative value?

Answer 25

its a positive force in the opposite direction

Question 26

if you know force F(t), what should you use to calculate a(t) and integrate to v(t) and p(t)

Answer 26

newtons second law

Question 27

what is x=0 regarding springs?

Answer 27

the position of the object when the spring is at resting length - the force applied to the object by the spring is zero

Question 28

what eq represents the force applied to the object by the spring?

Answer 28

-kx - k = the spring stiffness

Question 29

how can you calculate k (force stiffness)?

Answer 29

k = F/deformation L - apply force F to the end of the spring to measure deformation L

Question 30

stanford model

Answer 30

applicable to an entire muscle - active contraction initiated by action potential in muscle cell

Question 31

EMG (electromyography)

Answer 31

ions move across cell membrane which can detect electrical signals when muscle is activated - can cause contraction by applying voltage on membranes

Question 32

what 4 variables does force generation on muscle depend on?

Answer 32

1. strength (size of muscle) 2. activation (measured by emg signal) 3. length (shortest vs longest) 4. muscle velocity (speed of lengthening or shortening)

Question 33

what is the Fmusc equation?

Answer 33

F = Fiso x (a x fl(l) x fv(v) + fp(l))

Question 34

what is the equation for fl(l)?

Answer 34

fl(l) = - (l - 1)^2 + 1

Question 35

what is the equation for fv(v)?

Answer 35

fv(v) = 0.75cos[pi/2(v + 1)] + 0.75

Question 36

what is the equation for f=(l)?

Answer 36

fp(l) = 0.25e^l - 0.25

Question 37

end card

Answer 37

:)