Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Phys110 > (Phys110) Exam 2 Flashcards > Flashcards

(Phys110) Exam 2 Flashcards

1
Q

what is gravity?

A
  • a force that exists in every problem unless told otherwise (like if the object was in space/on a different planet)
  • Fg = mg
  • its vector always points downwards
  • long range force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is spring force?

A
  • a restorative force
  • when compressed the vector points in the direction that the object would move if it were to decompress (pushing force)
  • when stretched, the vector points in the direction that the object would move if the spring were to compress (pulling force)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is tension?

A
  • acts when a rope, string, or cable is attached to the object of interest
  • the vector always points away from the object
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is normal force?

A
  • when the object is on top of or attached to something
  • the vector always points perpendicular to the surface that the object is on top of or attached to
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is kinetic friction?

A
  • resistive force that resists motion and the object must be in contact with a surface - the vector points opposite the direction that the object moves, is parallel to the surface, and is perpendicular to normal force
  • Kinetic = moving
  • sliding/skidding
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is static friction?

A
  • a force that prevents slipping and the object must be in contact with a surface
  • the vector points opposite the direction that the object would move if it did move, is parallel to the surface, and is perpendicular to normal force
  • Static = not moving
  • Acts as a propulsion for walking and vehicles that are driving
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is drag?

A
  • air resistance/resistive force like kinetic friction but for air
  • ignore unless told otherwise (applies when the problem says “air resistance is not negligible”)
  • the vector points opposite the direction of motion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is newton’s 2nd law?

A
  • FBDs and the summation of forces in the x direction and y direction
  • Note: every summation of forces is set equal to “ma”. It is up to you to figure out what acceleration is based on what the problem tells you.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is dynamic equilibrium?

A

when an object is moving at a constant speed (a = 0)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is static equilibrium?

A

when the object is at rest (v = 0, a = 0)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

when do you set a summation of forces equal to “ma”?

A

always. every summation of forces is set equal to “ma”. It is up to you to figure out what acceleration is based on what the problem tells you.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is newton’s 3rd law?

A
  • If an object exerts a force on another object, then that other object exerts the same force back on the original object (2 or more objects)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are the 2 first steps to solving every problem (minus circular motion)

A
  1. Draw FBD (draw force identification diagram if you struggle with identifying forces that act on an object)
  2. Write N2L
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how do you know if forces are interaction pairs?

A
  • Two objects are an interaction pair if…
    > They are the same in nature
    > They have equal magnitudes
    > They have opposite directions
  • you can easily see which forces are interaction pairs in an interaction diagram (the objects will be connected by these interaction force pairs)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is max static friction?

A
  • whatever it needs to be (lol)
  • if it is overcome, static friction turns into kinetic friction
  • can be used as a check to see if an object moves or not
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the difference between a massless rope and a rope that has mass?

A
  • Massless: not an object - just connects objects in a system - doesn’t need its own FBD
  • has mass: is an object - needs its own FBD
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is the r - axis?

A
  • radial direction
  • points away from the particle/object, toward the center of the circle
  • velocity in r-direction is zero
  • acceleration in the r-direction is not zero (on formula sheet a_r)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is the t - axis?

A
  • tangential direction
  • is tangent to the circle, pointing in the CCW direction
  • velocity in t-direction is zero
  • acceleration in t-direction is zero
  • only used in vertical circular motion problems
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the z - axis?

A
  • perpendicular to the plane of motion (above or below the plane of motion)
  • velocity in z-direction is zero
  • acceleration in z-direction is zero
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

when an object travels in uniform circular motion, does it have constant speed?

A

no
- Fnet = ma = (mv^2)/r

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

how do you know if you’re dealing with a N3L problem?

A

when two or more objects are interacting with each other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

a steal beam hangs from a cable as a crane lifts the beam. what forces act on the beam?

A

gravity and tension in the cable
> think about what touches the beam (drawing force identification diagram would help)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

a bobsledder pushes her sled across horizontal snow to get it going, then jumps in. after she jumps in, the sled gradually slows down to a halt. what forces act on the sled just after she’s jumped in?

A

gravity, normal force, and kinetic friction
> drawing force identification diagram would help

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

a ball rolls down an incline and off a horizontal ramp. ignoring air resistance, what force(s) act on the ball as it moves through the air just after leaving the horizontal ramp?

A

gravity acting vertically down
> drawing a force identification diagram would help
> think about what is contact with the ball

25
Q

an object attached to a rope is lowered at a constant speed. which is true?
a. the rope tension is greater than the object’s gravitational force
b. the rope tension equals the object’s gravitational force
c. the rope tension is less than the object’s gravitational force
d. the rope tension can’t be compared to the object’s gravitational force

A

b. the rope tension equals the object’s gravitational force
> constant motion means no acceleration
> summation of forces equals zero
> Fy: T - mg = 0
> T = mg

26
Q

an object attached to a rope is lowered at a steadily decreasing speed. which is true?
a. the rope tension is greater than the object’s gravitational force
b. the rope tension equals the object’s gravitational force
c. the rope tension is less than the object’s gravitational force
d. the rope tension can’t be compared to the object’s gravitational force

A

a. the rope tension is greater than the object’s gravitational force
> not constant motion means acceleration is not zero
> summation of forces equals “ma”
> Fy: T - mg = ma
> T = ma + mg
> Fg = mg
T < mg

27
Q

how can you find the weight of something?

A
  • draw FBD
  • write N2L
  • solve for normal force
28
Q

car B is stopped for a red light. car A, which has the same mass as car B, doesn’t see the red light and runs into the back of car B. which of the following is true?
a. B exerts a force on A but A doesn’t exert a force on B
b. B exerts a larger force on A than A exerts on B
c. B exerts the same amount of force on A as A exerts on B
d. A exerts a larger forces on B than B exerts on A

A

c. B exerts the same amount of force on A as A exerts on B
> cause newton says so
> N3L problem: there are two objects interacting and the forces are equal and opposite

29
Q

a small car is pushing a larger truck that has a dead battery. the mass of the truck is larger than the mass of the car. which of the following is true?
a. the car exerts a force on the truck but the truck doesn’t exert a force on the car
b. the car exerts a larger force on the truck than the truck exerts on the car
c. the car exerts the same amount of force on the truck as the truck exerts on the car
d. the truck exerts a larger force on the car than the car exerts on the truck

A

c. the car exerts the same amount of force on the truck as the truck exerts on the car
> cause newton says so
> N3L problem: there are two objects interacting and the forces are equal and opposite

30
Q

should you practice drawing FBDs, writing N2L, drawing interaction diagrams, and drawing force identification diagrams?

A

yes lol please do. the force identification diagrams are optional but still helpful.

31
Q

a box on a rough surface is pulled by a horizontal rope with tension T. the box is not moving. in this situation:
a. fs > T
b. fs = T
c. fs < T
d. fs = 0

A

b. fs = T
> not moving means the system is in static equilibrium so the summation of forces is equal to zero
> Fx: T - fs = 0
> T = fs

32
Q

a box with a weight of 100N is at rest. It is then pulled by a 30N horizontal force. Does the box move?
a. yes
b. no
c. not enough info

A

b. no
> check if an object moves by using the equation for max static friction
> fs = us*n
> compare to pulling force

33
Q

a box is being pulled to the right over a rough surface. T > fk, so the box is speeding up. suddenly, the rope breaks. what happens? the box…
a. stops immediately
b. continues speeding up for a short while then slows and stops
c. keeps its speed for a short while then slows and stops
d. slows steadily until it stops

A

d. slows steadily until it stops
> when the rope breaks, the agent is gone
> force identification diagram would help
> cannot make an object immediately stop, it takes some time to stop
> Fx: -fk = ma

34
Q

how do you know if an object is slowing down?

A

when velocity and acceleration vectors point in opposite directions

35
Q

how do you know if an object is slowing down?

A

when velocity and acceleration vectors point in the same direction

36
Q

how can you tell what direction an object is moving?

A
  • read the problem
37
Q

what do you need to solve for if a problem says “how far does an object move” or “how far apart…?”

A

position (delta s, delta y, or delta x)

38
Q

what do you need to solve for if a problem says “how fast is the object”

A

velocity (v, vi, or vf)

39
Q

what do you need to solve for when a problem says “does the object move?”

A

use fs_max to check to see if the object moves and compare it with whatever force is trying to make the object move

40
Q

what do you need to solve for when a problem says “how long does it take…?”

A

time (t)

41
Q

what does the unit “m/s” belong to?

A

velocity (v)

42
Q

what does the unit “m/s^2” belong to?

A

acceleration (a)

43
Q

what does the unit “s” belong to?

A

time (t)

44
Q

what does the unit “rad/s” belong to?

A

angular velocity (w - omega)

45
Q

what does the unit “rpm” belong to?

A

angular velocity (w - omega)
> convert to rad/s

46
Q

what does T stand for?

A
  • tension
  • period (circular motion)
47
Q

in what kind of problems is the t - axis used ?

A

vertical circular motion problems only

48
Q

what happens to normal force at the bottom of a loop?

A

normal force is bigger than gravity because it needs to support the weight in order to maintain circular motion with centripetal acceleration - working against gravity

49
Q

what happens to normal force at the top of a loop?

A

normal force is smaller than gravity because it works with gravity to maintain circular motion - normal force is also a pushing force and we don’t want a pushing force being big, otherwise the object will fall

50
Q

what direction does normal force point when you are at the top of a loop-the-loop roller coaster?

A

down - the cart is attached to the bottom of the track and normal force always points perpendicular to the surface it’s attached to/on top of

51
Q

what direction does normal force point when you are at the bottom of a loop-the-loop roller coaster?

A

up - cart is on top of the track and normal force is always perpendicular to the surface it’s attached to/on top of

52
Q

what are your first steps in solving circular motion problems?

A

step 0: visualize the problem with a force identification diagram (this will also help you figure out how to label your axes)
step 1: draw FBD (make sure the axes are labelled correctly: rtz-coordinate system)
step 2: write N2L (make sure summations are labeled correctly: Fz, Fr, etc)
etc

53
Q

two coins are on a turntable that steadily speeds up, starting from rest, with a ccw rotation. which coin flies off the turntable first? (coin 1 is closer to the center of the circle in comparison to coin 2)
a. coin 1
b. coin 2
c. both at the same time
d. can’t say without knowing their masses

A

b. coin 2
> a greater radius means max static friction is reached faster

54
Q

if a question asks for the push force at the bottom of a vertical motion ride, what do you solve for?

A

normal force

55
Q

if a question asks for the push force at the top of a vertical motion ride, what do you solve for?

A

normal force

56
Q

how do you convert rpm to rad/s?

A

if you don’t know, go look at the notes i’ve sent lol i cant type it here (i wouldnt stress abt this too much; if you do need to convert on the test and cant remember, js go ask him, he should tell you) (still good to practice tho)

57
Q

how do you convert rad/s to rpm?

A

if you don’t know, go look at the notes i’ve sent lol i cant type it here (i wouldnt stress abt this too much; if you do need to convert on the test and cant remember, js go ask him, he should tell you) (still good to practice tho)

58
Q

when should you draw an interaction diagram?

A

whenever two objects are interacting with each other - make sure to label everything properly

Phys110 (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions