Newton's 1st & 3rd Laws

Question 1

Newton’s 1st Law of Motion

Law of Inertia

Answer 1

Any object will remain at rest or moving with uniform motion (constant speed AND constant direction) iff the net force acting on that object is zero.

OR

A net force acting on an object will cause that object to accelerate (change its motion by changing its speed and/or direction).

a = f/m ⇒ responsiveness to force = net force/inertia

Question 2

inertia

Answer 2

responsiveness of an object to force

Question 3

inertia & mass

Answer 3

The measure of an object’s inertia is the object’s mass.

The more mass an object has, the more inertia it has, and the less it responds to force.

Question 4

canceling a force

Answer 4

Only a force can resist/cancel another force. Mass(inertia) by itself cannot resist force.

When an obj appears to resist a force cuz it doesn’t accelerate in response 2 the force, always cuz another force is acting. usually friction.

Question 5

Greek philosopher Aristotle asserted that

Answer 5

force is required for motion

heavier objects fall faster than lighter objects

Question 6

the acceleration of an obj is due to

Answer 6

an unbalanced force acting on the object

Question 7

An object following a striaght-line path at a constant velocity must

Answer 7

have zero acceleration

still forces, just canceled out

Question 8

A moving truck is traveling down the road at constant velocity. Inside the storage compartment, a rock is dropped from the midpoint of the ceiling and strikes the floor below. The rock hits the floor

Answer 8

exactly below the midpoint of the ceiling

part of the system

same velocity

Question 9

passenger in car moving in straight line at constant speed

car turns sharply to left and u’re thrown against side door

Answer 9

When a passenger is wearing a seatbelt, basically share the same state of motion as the car. accelerate and decelerate with car.

when not wearing seat belt, seaparte objects with separate rates of motion. when the car abruptly changes direction, the passenger continues with the same velocity as before (until they hit the door)

Question 10

Newton’s 3rd Law of Motion

Answer 10

For every force there is an equal and opposite reaction force.

F_AonB = -F_BonA

Question 11

action-reaction pair

Answer 11

the 2 forces involved

do not cancel each other

Question 12

“equal”

Answer 12

equal in magnitude

occur @ exactly the same time & last for same amount of time - simultaneous

Question 13

“opposite”

Answer 13

oppsoite in direction

180o

Question 14

Why don’t action and reaction forces cancel each other out?

Answer 14

They are usually acting on different objects.

Question 15

where do you draw vectors?

Answer 15

on the object receiving the force

Question 16

Why does Bob meat Annie in tug of war?

Answer 16

Based on Newton’s 3rd Law, they are both exerting the same amount of force, but Bob still winds because he is exterting more force on the ground

Question 17

If the floor is exerting a reaction force back on you due to your weight on it, then why don’t you get pushed into the air away from the floor?

Answer 17

Gravity pushes you down.

Question 18

If a horse exerts a force on the cart & the cart exerts an equal but opp force on the horse, how can the horse move the cart?

Answer 18

There are more than just the 2 forces acting on the horse and cart.

Also, the 2 forces are both acting on different objects with different masses.

Question 19

when can action-reaction forces cancel each other out?

Answer 19

if they are part of the same system and become internal forces

Question 20

drawing tug of war vectors

Answer 20

rope on gm -> rope on gp <-

gm on rope <- gp on rope ->

earth on gm v gm on earth ^

earth on gp v gp on earth ^

ground on gm(ground helping gm) <- gm on ground ->

ground on gp -> gp on ground <-

ground on gm ^ gm on ground v

ground on gp ^ gp on ground v