Physics Unit 2 - Forces

Question 1

Fn

Answer 1

surface force

Question 2

Ffr

Answer 2

force of friction (opposing motion)

Question 3

Fap

Answer 3

Push/pull exerted by an object

Question 4

Fg

Answer 4

Gravitational force (attraction between two objects)

Question 5

Ft

Answer 5

Tension force pulled by a rope/string/chain

Question 6

Balanced Force

Answer 6

A force with an acceleration or Fnet of 0
Either motionless or constant velocity

Question 7

Unbalanced Forces

Answer 7

Forces act on an object. Fnet does NOT equal 0 and object has an acceleration

Question 8

Newton’s First Law (Inertia)

Answer 8

If object is motionless, it stays motionless (unless moved by another force)
If object is in constant motion, object stays in motion (Unless an opposing force)

Question 9

proportionality for Inertia and mass

Answer 9

Directly Proportional

Question 10

Standing on a bus that suddenly moves [F]

Answer 10

Before= Object @ rest, stays @ rest
After= Another force pushes and person is “left behind”

Question 11

Seatbelts

Answer 11

Car suddenly stops, car decelerates fast, but body wants to continue moving (inertia- 1)
Seatbelt gives external force that opposes inertia and decelerates body as car slowd down

Question 12

Seatbelt mechanism

Answer 12

Moves constantly with the car
When it feels a pull [B], pedulum blocks spinner, locking the seatbelt in place
This makes it act as an external opposing force for the body

Question 13

Headrest

Answer 13

Rear-end collisions: vehicle decelerates fast, inertia makes body continue [F]
Body strapped in by a seatbelt, head and neck have no support making it have an unnatural position (whiplash).
Headrest counter acts inertia by limiting heads movements during collision

Question 14

Crumple Zone

Answer 14

Front of the Car “Crumple Zone” : absorbs impact of collision
Slows time it takes to stop the vehicle, applies less force on passengers
(2nd Law - a is inversely proportional to mass, directly proportional to Fnet)

Question 15

Newton’s Second Law

Answer 15

Object will accelerate in unbalanced force’s direction
Fnet and A = DIRECT
Fnet and m = INDRECT
m and A = INDIRECT

Question 16

How much is one Newton

Answer 16

1N = kg x m
———-
s^2

Question 17

Newton’s Third Law

Answer 17

Positive Action = Negative Reaction

Question 18

Friction

Answer 18

Horizontal forces that opposes motion of an object when two surfaces are in contact

Question 19

Why does friction happen?

Answer 19

B/c of microscopic irregularities between two surfaces (IMF forces and “surface welds”)

Question 20

Static friction (Fs)

Answer 20

opposes the start of motion (highest IMF and surface welds)

Question 21

Kinetic friction (Fk)

Answer 21

Opposes movement of moving objects (lower surface welds)

Question 22

Coefficient of friction (mew)

Answer 22

Constant ratio and %
ALways positive
Larger mew = more friction between surfaces,
opposite for smaller mew

Question 23

proportionality for mew, Ffr and Fn

Answer 23

mew DIRECT Ffr
mew DIRECT Fn
Ffr DIRECT Fn