Motion And Force

Question 1

Vector

Answer 1

Physical quantity with both magnitude and direction.

Question 2

How to add vectors

Answer 2

Place the first vector such that the head of the arrow meets the tail of the second vector, and draw an arrow from the tail of the first to the head of the second.

Question 3

How to subtract vectors

Answer 3

Place the heads of the two vectors together and draw an arrow from the tail of the first to the tail of the second.

Question 4

Component vectors

Answer 4

Always at right angles to each other, and their sum is equal to the vector being replaced.

Question 5

Pythagorean theorem

Answer 5

A2+B2=C2
SOH CAH TOA
Opp=Hsin(angle)
Adj=Hcos(angle)

Question 6

Translational motion

Answer 6

Speed=distance/time
Velocity =displacement/time 
Acceleration =change in velocity/time 
X-Xo=Vot+1/2at2
V-Vo=at
V2=Vo2+2a(X-Xo)
Vavg =1/2(V+Vo)

Question 7

Scalar

Answer 7

Physical quantity that has magnitude but no direction.

Question 8

Displacement vs time graph

Answer 8

Slope = instantaneous velocity at that time.
Upward slope = positive velocity; downward slope = negative velocity (velocity in the reverse direction)
Straight line = constant velocity (straight horizontal line = slope of 0 = not moving). Curved line = changing velocity = acceleration.
Area beneath curve has no meaning.

Question 9

Velocity vs time graph

Answer 9

Slope = instantaneous acceleration at that time.
Upward slope = positive acceleration; downward slope = negative acceleration (acceleration in the reverse direction).
Straight line = constant acceleration; curved line = changing acceleration.
Area beneath curve = distance (label all area between curve and zero velocity as positive) or displacement (label area below zero velocity as negative)

Question 10

Gravitational acceleration

Answer 10

~10 m/s2

Question 11

Projectile motion

Answer 11

Initial vertical velocity (or Vo sin angle) is equal to the square root of 2gh, where g is positive 10 m/s2 and h is peak height. Can also use this equation to find final velocity v of a projectile that is dropped straight down from a height h.
Mass does not affect projectile motion assuming that there is no air resistance.

Question 12

Inertia

Answer 12

The tendency of all objects to remain in their current state of motion, whether they are moving or at rest.

Question 13

Mass

Answer 13

Quantitative measure of an object’s inertia; how much that object will resist a change in its motion. Usually measured in kg.

Question 14

Weight

Answer 14

Gravitational force that an object experiences when it is close to a much larger body, such as the earth. Measured in newtons (N).
Weight at surface of earth = mg

Question 15

Center of mass

Answer 15

Point at which all of the system’s mass can be considered to be concentrated. Center of mass of an object doesn’t have to be located within that object.

Question 16

Net force

Answer 16

The sum of all forces acting on an object. Two forces that are equal in magnitude but opposite in direction will cancel each other out, leaving zero net force.
Net force, think acceleration.

Question 17

Force

Answer 17

Causes and changes motion. Four types of force in nature: strong nuclear force; weak nuclear force; gravitational force; electromagnetic force. First two exist only within nucleus of an atom.
Contact forces are electromagnetic.

Question 18

Newton’s first law of motion

Answer 18

Inertia

Question 19

Newton’s second law of motion

Answer 19

F=ma, F and a are directly proportional.

Question 20

Newton’s third law of motion

Answer 20

For every action, there exists an equal and opposite reaction

Question 21

Newton’s law of universal gravitation

Answer 21

F=G(m1m2/r2) where G=6.67x10-11 m3kg-1s-2.

Question 22

Inclined planes

Answer 22

Normal force equals mg cos (angle).

Net force due to gravity and the normal force equals mg sin (angle) and is parallel to the plane.

Question 23

Friction

Answer 23

Force that opposes relative motion.
Common type of friction is drag, aka air resistance.
More massive objects are less affected by air resistance than less massive objects.

Question 24

Hooke’s law

Answer 24

Applies to compression or stretching an object.
F=-k (change in position), where k is a constant unique to a given object.
Most often applied to springs.