Ch. 1: Kinematics and Dynamics

Question 1

SI Units

Answer 1

Related to the metric system include meter, kilogram, second, ampere, mole, kelvin, and candela

Question 2

Vectors

Answer 2

Physical quantities that have both magnitude and direction. Include displacement, velocity, acceleration, and force, among others

Question 3

Scalars

Answer 3

Quantities without direction. May be the magnitude of vectors (like speed) or may be dimensionless, like coefficients of friction

Question 4

Vector addition

Answer 4

Use the tip to tail method or break vector into components, add x components and add y components to get x and y components of resultant vector and use the Pythagorean theorem to find resultant

Question 5

Vector subtraction

Answer 5

change the direction of the subtracted vector and then follow the procedures for vector addition

Question 6

Finding the x and y components of a vector

Answer 6

x= Vcosθ
y= Vsinθ; θ is angle between x component and vector
If we know x and y we can find V using pythagorean theorem

Question 7

Multiplying a vector by a scalar

Answer 7

Changes the magnitude and may reverse the direction

Question 8

Multiplying a vector by a vector

Answer 8

Dot product: scalar quantity, product of the vectors magnitudes and the cosine of the angle between them
Cross product: vector quantity. Product of the vectors magnitudes and the sine of the angle between them. Right hand rule is used to determine direction of resultant vector

Question 9

Displacement

Answer 9

Vector representation of a change in position. Path independent and is equivalent to the straight line distance between the start and end locations

Question 10

Distance

Answer 10

Scalar quantity that reflects the path traveled

Question 11

Velocity

Answer 11

Vector representation of the change in displacement with respect to time

Question 12

Average velocity

Answer 12

Total displacement divided by total time

Question 13

Average speed

Answer 13

Total distance divided by total time

Question 14

Instantaneous velocity

Answer 14

Limit of the change in displacement over time as the change in time approaches 0

Question 15

Instantaneous speed

Answer 15

Magnitude of the instantaneous velocity vector

Question 16

Force (F)

Answer 16

Any push or pull that has the potential to result in an acceleration. SI unit for force is newton (N) = (kg*m)/s^2

Question 17

Gravity

Answer 17

Attractive force between 2 objects as a result of their masses

Question 18

Gravitational force

Answer 18

Fg = (Gm1m2)/r^2; m1 = mass of object 1, m2 = mass of object 2, G is universal gravitational constant, r =dist between centers of mass

Question 19

Friction

Answer 19

Force that opposes motion as a function of electrostatic interaction at the surfaces of 2 objects

Question 20

Static friction (fs)

Answer 20

Exists between two objects that are not in motion relative to each other– can take on many values depending on magnitude of an applied force

Question 21

Coefficient of static friction

Answer 21

Unitless quantity that is dependent on the two materials in contact
0 ≤ fs≤usN; us = coefficient of static friction, N=magnitoude of normal force

Question 22

Normal force

Answer 22

Component of the force between two objects in contact that is perpendicular to the plane of contact between the object and the surface upon which it rests

Question 23

Kinetic friction (fk)

Answer 23

Exists between two objects that are in motion relative to each other, a sliding object and surface over which object slides; constant value=ukN=f

Question 24

Coefficient of friction

Answer 24

Depends on the two materials in contact. The coefficient of static friction is always higher than the coefficient of kinetic friction.

Question 25

Mass (m)

Answer 25

Measure of the inertia of an object– amt of matter in the object. Scalar quantity so only has a magnitude. SI unit is kilogram (kg), independent of gravity

Question 26

Weight (Fg)

Answer 26

Force experienced by a given mass due to its gravitational attraction to the earth, vector quantity w units in newtons (N), weight of an object can be thought of as being applied at a single point in that object called the center of mass or gravity

Question 27

Relation between weight and mass

Answer 27

Fg= mg; g is acceleration due to gravity (9.8 m/s^2)

Question 28

Acceleration

Answer 28

Vector representation of the change in velocity over time. Average or instantaneous acceleration may both be considered, similar to velocity. Average acceleration is defined as ā = Δv/Δt; instantaneous acceleration is defined as avg acceleration as Δt approaches 0

Question 29

Newton’s first law

Answer 29

Law of inertia: states than an object will remain at rest or move with a constant velocity if there is no net force on the object

Question 30

Newton’s second law

Answer 30

States that any acceleration is the result of the sum of the forces acting on the object and its mass

Question 31

Newton’s third law

Answer 31

States that any 2 objects interacting w one another experience equal and opposite forces as a result of their interaction

Question 32

Linear motion

Answer 32

Includes free fall and motion in which the velocity and acceleration vectors are parallel or anti parallel

Question 33

Air resistance

Answer 33

Opposes the motion of an object; object in free fall will experience a growing drag force as the magnitude of its velocity increases. Eventually this drag force will be equal in magnitude to the weight of the object nand the object will fall with constant velocity according to Newton’s first law; this velocity is called terminal velocity

Question 34

Projectile motion

Answer 34

Contains both an x- and y- component. Assuming negligible air resistance, the only force acting on the object is gravity

Question 35

Inclined planes

Answer 35

Example of 2D motion. Easiest to consider the dimensions as being parallel and perpendicular to the surface of the plane

Question 36

Circular motion

Answer 36

Has radial and tangential dimensions. Fc = (mv^2)/r

Question 37

Uniform circular motion

Answer 37

only force is centripetal force pointing radially inward. Instantaneous velocity vector always points tangentially

Question 38

Dynamics

Answer 38

Study of forces and torques

Question 39

Free body diagram

Answer 39

Representations of the forces acting on an object. Useful for equilibrium and dynamics problems

Question 40

Translational Equilibrium

Answer 40

Occurs in absence of any net forces acting on an object. An object in translational equilibrium has a constant velocity, and may or or may not also be in rotational equilibrium

Question 41

First condition of equilibrium

Answer 41

Translational equilibrium only exists when vector sum of all of the forces acting on an object is 0 (same as newton’s first law)

Question 42

Rotational equilibrium

Answer 42

Occurs in the absence of any net torques acting on an object. Rotational motion may consider any pivot point, but the center of mass is most common. An object in rotational equilibrium has a constant angular velocity– on mcat, usually 0

Question 43

Fulcrum

Answer 43

Fixed pivot point around which an object rotates

Question 44

Torque

Answer 44

Application of force at some distance from the fulcrum generates torque or the moment of force. Distance between applied force and the fulcrum is the lever arm. Torque generates rotational motion, not application of force itself