# Lecture 17 - Force and Motion Flashcards

1

Q

what are the 4 attributes of a vector?

A

- magnitude (speed)
- direction (heading)
- point of application (CoG)
- line of action

2

Q

what is the difference between velocity and speed?

A

- velocity is a vector
- speed is scalar
- velocity is the rate of change with respect to time (how long it takes to get from point a to b)

3

Q

what is average velocity?

A

- (s2-s1)/(t2-t1)
- delta s / delta t
- measured in m/s or km/hr
- assuming she is running at a constant speed
- measure s1 and s2 very close together (to avoid change of speed problems)

4

Q

what is instantaneous velocity?

A

- when you measure s1 and s2 where dt = 0
- v = ds/dt
- in m/s or km/h
- we lose no information, this tells us our expact speed at that time

5

Q

why is measuring average velocity over an entire race not an accurate measurement of speed?

A

- acceleration and deceleration phase are not accounted for
- deceleration will occur after ~70m (or you are not reaching max speed)

6

Q

what is cyclic velocity?

A

- the average velocity if an activity is cyclic
- ex: running, swimming, etc.
- v = distance per cycle x (# cycles/minute)

7

Q

what is acceleration vs negative acceleration?

A

- acceleration = speeding up
- negative acceleration = slowing down

8

Q

what is average acceleration?

A

- a = delta v / delta t
- unit = m/s^2
- instantaneous velocity at two different times

9

Q

what is instantaneous acceleration?

A

- instantaneous velocity at two times that are infinitesimally close together
- a = dv / dt
- unit = m/s^2

10

Q

how does gravity contribute to acceleration?

A

- always acting on the body’s COG
- g = 9.81m/s^2
- aka speeding up by 9.81m/s every second of falling

11

Q

how is force of gravity related to weight?

A

- proportional
- no matter what size, the object will fall at the same pace

12

Q

what is terminal velocity?

A

- free-falling at a constant acceleration of g
- drag increases as speed increases
- acceleration is zero, speed is constant (for terminal)
- stop of acceleration because speed is constant

13

Q

why does velocity have a parabolic motion?

A

- vertical component is always accelerating downwards at g
- horizontal component is constant
- these components behave differently

14

Q

what is newton’s 2nd law for constant mass?

A

- F = ma
- as force increases, acceleration will also increase assuming mass stays the same

15

Q

what is newton’s 2nd law for constant force?

A

- if force is the same, the more massive object will have a smaller acceleration