Mechanics key terms

Question 1

inertia

Answer 1

the property of an object to resist changes in motion

Question 2

What does acceleration depend on?

Answer 2

force, friction, inertia

Question 3

what does friction not depend on?

Answer 3

speed, area of contact

Question 4

what does drag depend on?

Answer 4

speed, area of contact

Question 5

mass

Answer 5

the quantity of matter in an object

- also the measure of inertia or sluggishness that the object exhibits, in response to any action impelled upon it

Question 6

Define weight

Answer 6

the force of gravity upon an object

Question 7

true or false; acceleration of free fall is independent of the objects’ mass

Answer 7

true

Question 8

in a vacuum, a coin and a feather fall equally side by side. Would it be correct to say that equal forces of gravity act on both the coin and the feather when it is in the vacuum?

Answer 8

no. these objects accelerate equally not because the forces of gravity are equal but because the ratios of their weights to masses are equal

Question 9

When does non free fall occur?

Answer 9

when the acceleration is less than g; due to resistive forces

Question 10

When is terminal speed/velocity reached?

Answer 10

when a= 0

Question 11

What is Newton’s first law?

Answer 11

every object must continue to be at a state of rest or move in uniform motion in a straight line unless compelled to change by forces impressed upon it

Question 12

What is Newton’s second law?

Answer 12

F= ma; a= f/m

Question 13

what is Newton’s third law?

Answer 13

Every action has an equal and opposite reaction

Question 14

a small mass would have a larger acceleration?

Answer 14

true

Question 15

a bigger mass would have a smaller acceleration?

Answer 15

true

Question 16

What is a projectile?

Answer 16

Any object that moves through the air or through space under the INFLUENCE OF GRAVITY

Question 17

What is the curved path the result of ?

Answer 17

the combination of horizontal and vertical components

Question 18

true or false; horizontal component of motion is completely independent of the vertical component of motion?

Answer 18

true

Question 19

What shape is the path of a projectile?

Answer 19

hyperbola

Question 20

If a projectile was launched how much does it does it drop and when?

Answer 20

vertical distance drops 5m for every 8 km

Question 21

Question: satellites remain in orbit instead of falling to the Earth because they are beyond the main pull of Earth’s gravity?

Answer 21

No, if moving objects were beyond the pull of gravity, it would move in a straight line and would not curve around the Earth; Satellites remain in orbit because they are being pulled by gravity; not because they are beyond it

Question 22

true or false; a satellite moves in a circular orbit, moving in a direction perpendicular to the force of gravity that acts on it

Answer 22

true

Question 23

what would happen to a projectile that is launched with a horizontal speed greater than 8km/s?

Answer 23

it will overshoot a circular path and trace an oval path called an ellipse

Question 24

why does weightlessness seem to occur?

Answer 24

when two objects accelerate at the same rate

Question 25

Define momentum (p)?

Answer 25

the property of moving things; inertia in motion

Question 26

true or false; an object at rest has no momentum?

Answer 26

true; it's not in motion; momentum is not something an object has but something it can provide

Question 27

define impulse (I)

Answer 27

change in momentum

Question 28

true or false; in an interaction, impulses are equal and opposite

Answer 28

true

Question 29

true or false; whenever you exert a net force, you also exert an impulse

Answer 29

true

Question 30

When does impulse = momentum

Answer 30

when the initial momentum is zero

Question 31

is an object brought to rest when impulse = initial momentum?

Answer 31

yes

Question 32

how do we change the momentum of an object?

Answer 32

we must apply an impulse

Question 33

What forces can cause an object to accelerate? internal or external forces?

Answer 33

external forces; which are forces applied from outside the system

Question 34

Is change in momentum possible if there is no external force present?

Answer 34

No

Question 35

when is momentum conserved (no momentum gained and no momentum lost)

Answer 35

Momentum is conserved in a closed system where no external forces are acting

Question 36

true or false; momentum is conserved in collisions

Answer 36

true; this means that the net change in momentum of system in colliding objects is unchanged before and after the collision

Question 37

why is momentum conserved in a collision?

Answer 37

this is because the forces that act DURING the collision are internal forces ( the existing momentum is just redistributed)

Question 38

what are the two types of collision?

Answer 38

elastic and inelastic

Question 39

What does elastic collision mean

Answer 39

colliding objects REBOUND without lasting deformation and generation of heat

Question 40

what does inelastic collision mean?

Answer 40

characterized by lasting deformation or the generation of heat or both

Question 41

What happens in a perfectly inelastic collision

Answer 41

the objects stick together (however momentum is conserved as well even when colliding objects become entangled

Question 42

what is energy

Answer 42

the property of system that enables it to do WORK

Question 43

What is power

Answer 43

rate of work

Question 44

What is energy measured in?

Answer 44

Joules

Question 45

Define mechanical energy

Answer 45

the form of energy relative to the position of the interacting bodies (potential energy) or their motion

Question 46

What are the forms of mechanical energy?

Answer 46

Kinetic energy potential energy or both

Question 47

What is potential energy

Answer 47

the stored energy due to an objects' position relative to another object

Question 48

What is gravitational potential energy (GPE)

Answer 48

the potential energy of a body due to elevated positions (GPE = mgh)

Question 49

define kinetic energy

Answer 49

energy of motion; depends on the reference frame; always positive

Question 50

true or false; only part of the total work that you do in changing the objects' KE, the rest is going to heat

Answer 50

true

Question 51

true or false; WORK is not a form of energy; but a way of transferring energy from one place to another or one form to another

Answer 51

true

Question 52

What is the law of conservation of energy?

Answer 52

Energy can neither be created nor destroyed; it may be transformed from one form into another ; but the total amount of energy never changes

Question 53

What is a machine

Answer 53

a machine is device for multiplying forces or simply changing the direction of the forces

Question 54

What is a fulcrum (imagine a triangle)

Answer 54

a point of support on which lever, rotates

Question 55

What does a pulley change

Answer 55

the direction of force input

Question 56

what happens when the fulcrum of a lever is relatively close to the load?

Answer 56

the small input force will produce a large output force. This is because the input force is exerted through a large distance and the load is moved over a corresponding short distance

Question 57

true or false; the forces acting on a machine can change, but the work input and work output will remain the same

Answer 57

true

Question 58

define efficiency

Answer 58

the percent of work input put into a machine that is converted to useful work output

Question 59

what happens when the efficiency of a machine is low

Answer 59

more of the work input is degraded to thermal energy

Question 60

when does inefficiency occur?

Answer 60

whenever energy in the world around is transformed from one form to another

Question 61

what happens when energy is transformed?

Answer 61

there is a dilution of USEFUL energy - the amount of usable energy decreases with each transformation until there is nothing left but thermal energy at ordinary temperature

Question 62

define RPM

Answer 62

revolutions per minute

Question 63

# Define rotational inertia - the property of an object to resist changes in rotational state of motion

Answer 63

an object rotating about an axis tends to remain rotating about the same axis unless inferred with by some external influence (torque)

Question 64

What does rotational inertia depend on?

Answer 64

distribution of MASS

Question 65

true or false; the greater the distance between the bulk of an object's mass and its' axis of rotation, the greater the rotational inertia

Answer 65

true