chapter 4/5 Forces

Question 1

Increase in mass provides a ________ acceleration

Answer 1

smaller

Question 2

Newton’s second law (equation)

Answer 2

F=ma

Question 3

2 kinds of forces

Answer 3

Contact force: forces that act on an object by touching it at a point of contact
Long-range forces: forces that act on an object without physical contact

Question 4

4 fundamental forces (weakest to strongest)

Answer 4

1. gravity- has the largest field of influence, equation: FG=m1m2/r^2 (G=6.67(10^-11), m1= mass of kg, m2=other object, r= how far away they are from each other)
2. electromagnetic force- occur between any two charged particles, causing an attraction between particles with opposite charges and repulsion between particles with the same charge, equation= FE= kq1q2/r^2 (k= Coulomb’s constant, q1= # of protons or electrons, q2= charge, r=distance between charges)
3. Weak force- regulates atomic decay
4. strong nuclear force- keeps protons together

Question 5

8 derived forces

Answer 5

1. push- FP
2. pull/tension- FT
3. normal- FN - perpendicular up
4. friction- FF - sliding force, due to properties of objects contact, static friction- nothing is moving but its trying to, kinetic- moving/sliding, rolling- rolling wheel
5. weight- FW, FW=mg, points to center of object
6. buoyant- FB=weight of fluid displaced, air is a fluid, FB=pVg (p=density, v=volume, g=gravity)
7. adhesive- 2 unlike things
8. cohesive- attracted to itself

Question 6

centripetal

Answer 6

walking toward center/middle, force responsible for making things move toward middle, not a force on its own- always supplied by something else (another force)

Question 7

spring restoring force

Answer 7

when pulled- goes back/ when compressed- pushes back

Question 8

centrifugal

Answer 8

-fictitious force, usually is just internal (not a force)

Question 9

Hooke’s Law

Answer 9

Fs= -kx
(spring force (y)= -spring constant (how strong spring is) x

Question 10

Newton’s first law

Answer 10

an object with no net force acting on it moves with a constant velocity
- also called law of inertia
- inertia: property of matter where is resists all changes in its state of motion

Question 11

Newtons second law

Answer 11

a=F/m
-more f more a
- a is directly proportional to F
- a is directly proportional to 1/m

Question 12

net force and acceleration…

Answer 12

go the same direction

Question 13

newtons third law

Answer 13

when 1 object exerts a force on a 2nd object, the 2nd object exerts a force on the the 1st that is equal in magnitude and opposite in direction
-every action has an equal and opposite reaction
- F=ma

Question 14

center of mass/gravity

Answer 14

-where you can assume all the mass is in an object- at the balance point
-center of mass does not have to be on an object, it can be in air

Question 15

what do bathroom scales measure?

Answer 15

normal force, not weight

Question 16

friction

Answer 16

-force that opposes any sliding motion
1. rolling friction
2. kinetic friction
3. static friction
equation: F= μFN

Question 17

is static friction more than kinetic?

Answer 17

no bc max is more, but it doesn’t mean static is always more

Question 18

with an incline problem

Answer 18

• flip sin and cos (cos for y, sin for x)

Question 19

static equallibrium

Answer 19

an object at rest

Question 20

dynamic equallibrium

Answer 20

an object moving in a straight line at a constant speed

Question 21

apparent weight

Answer 21

magnitude of supporting contact forces

Question 22

if a body is at rest or moving with a constant velocity, the sum of the forces acting on it is…

Answer 22

zero.