Newton's 2nd Law Quiz

Question 1

force

Answer 1

a push/pull on an object

transferred from one object to another

causes change in motion - does not cause motion (change in direction/speed)

not necessary to sustain motion

Question 2

inertia

Answer 2

responsiveness to force

no object can resist a force - only other forces can counter a force

indicated by mass: as mass goes up, inertia goes up, and acceleration responsiveness goes down

If an object is at rest, it tends to remain at rest. If it is moving at a constant velocity, it tends to continue moving at that velocity.

Question 3

Newton’s 2nd Law

Answer 3

f = ma

Question 4

what is the unit of force?

Answer 4

Newton (N) = kg•m/s²

Question 5

what equation can be derived from Newton’s 2nd Law?

Answer 5

a = fnet/mass

fnet being the vector sum of all forces acting on an object

Question 6

2D vector adding

Answer 6

• if at right angles, Pythogorean Theorem
• if not at right angle, form a parallelogram and then the diagonal coming from b/w the 2 vectors will be the resultant
• if not at right angle, can also split bottom vector into horizontal and vertical components and join them with top vector, add the parallel vectors, put the remaining vectors back together at a right angle, and then use Pythogorean Theorem

Question 7

if three motorboats r crossing a river and motorboat a’s resultant is straight across, b’s is closest to the opposite shore, and c’s is longest, then

a) which boat reaches the opposite shore first?
b) which boat provides the fastest ride?
c) which boat takes the shortest path to the opposite shore?

Answer 7

b

c

a

Question 8

how do u tell which resultant is fastest

Answer 8

longest

Question 9

weight

Answer 9

strength of the force of gravity on an object

unit of measure is N or lbs

measured by spring scale

W = mass•accel.fromgravity

depends on laction in a gravitational field

Question 10

mass

Answer 10

measure of amount of matter in an object and only depends on the number and kind of atoms that compose it

indicates inertia

measured by a balance

fundamental

unit = kg

Question 11

how are weight and mass related?

Answer 11

directly proportional

Question 12

how are force and acceleration related?

Answer 12

directly

Question 13

how are mass and acceleration related?

Answer 13

inverse relationship

Question 14

when doing the pulley and cart experiment, how do u calculate the acceleration?

Answer 14

force is the weight of attached to the end of the pulley

mass is the mass of the weights at end of pulley and mass of cart and any masses on cart

Question 15

what are the fundamental units that make up a Newton (N)?

Answer 15

kg • m

______

s²

Question 16

net force

Answer 16

the vector sum of all forces acting on an object

something that distrubs a state of equilibrium/changes the velocity of an object

Question 17

contact force

Answer 17

acts on an obj only by touching it

Question 18

long-range force

Answer 18

exerted w/out contact

Question 19

Friction (F_f)

Answer 19

the contact force that acts to oppose sliding motion b/w surfaces

parallel to surface & opp. direction of sliding.

Question 20

Normal (F_N)

Answer 20

the contact force exerted by a surface on an object

perpendicular to and away from the surface

Question 21

Spring (F_sp)

Answer 21

a restoring force, that is, the push or pull a spring exerts on an object

opposite the displacement of the object at the end of the spring

Question 22

Tension (F_T)

Answer 22

the pull exerted by a string, rope, or cable when attached to a body and pulled taut

away from the object and parallel to the string, rope, or cable at the point of attachment

Question 23

thrust (F_thrust)

Answer 23

a general term for the forces that move objects such as rockets, planes, cars, and people

in the same direction as the acceleration of the object barring any resistive forces

Question 24

Weight (F_g)

Answer 24

a long-range force due to graviational attraction between two objects, generally Earth and an object

straight down toward the center of Earth

Question 25

common misconceptions

Answer 25

• when a ball has been thrown, the force of the hand that threw it remains on it. NO, the force of the hand is a contact force; therefore, once contact is broken, the force is no longer exerted.
• A force is needed to keep an object moving. NO, if there is no net force, then the object keeps moving with unchanged velocity. if friction is a factor, then there is a net force and the object’s velocity will change.
• Inertia is a force. NO, inertia is the tendency of an obj to resist changing its velocity. forces are exerted on objects by the environment; they are not properties of objects.
• Air doesn’t exert a force. NO, air exerts a huge force, but because it is balanced on all sides, it usually exerts no net force unless an object is moving.
• the quantity ma is a force. NO, the equals sign in F = ma doesn’t define ma as a force. rather, means that exprmts have shwn tht the 2 sides of the equation or equal

Question 26

A ball is thrown straight up into the air. At the very top of its trajectory of motion (just before it starts to fall back down) the net force on the ball is

Answer 26

its weight

at the top, the only force acting on the ball is the force of gravity (same as weight)

Question 27

How do u calculate what friction force acts on a mass?

Answer 27

Ex: A horizontal force of 5.0 N accelerates a 4.0-kg mass, from rest, at a rate of 0.50m/s2 in the positive direction. What friction force acts on the mass?

1. Calculate normal force. F = ma. F = 4kg • 0.5m/s2 = 2N
2. Find the net force between 2N from previous step and given force (5N)
3. 5-2 = 3N

Question 28

equilibrium

Answer 28

An object is in equilibrium if it is at rest or if it is moving at constant velocity.