Physics - Forces And Newtons Laws

Question 0

Mass

Answer 0

The measure of the amount of matter in an object

Measured in kilograms

Question 1

Newton’s first law

Answer 1

Law of inertia - an object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an unbalanced force

Question 2

Inertia

Answer 2

The property of an object that describes how much it will resist change to the motion of the object

More mass = more inertia

Question 3

Microwelds

Answer 3

Occur when two bumpy surfaces are rubbed up against each other

Question 4

Newton’s second law?

Answer 4

F = m x a

Question 5

Weight (force) =

Answer 5

Mass x gravity (earth)

Weight is a measure of the force of gravity on the mass of an object

Question 6

Newton’s third law

Answer 6

For every action there is an equal and opposite reaction

Question 7

Fn =

Answer 7

The normal force

The supporting force that acts in the object perpendicular to the surface plane. It’s the portion of the weight of the object that is supported

Question 8

How to find friction force??

Answer 8

Ff = μFn

Ff = friction force (N)
μ = coefficient of friction 
Fn = normal force (N)

Question 9

Friction

Answer 9

The force that opposes motion between two surfaces that are touching each other

Question 10

An object at rest has what kind of acceleration?

Answer 10

Acceleration is 0

Question 11

If acceleration is zero…

Answer 11

Net force is equal to zero

Question 12

Tension

Answer 12

Pulling force exerted by the end of a string, rope, etc. on an object

Question 13

Steps to tension problems (5)

Answer 13

1. Set forces in x and y equal
   Ty + Ty = mg
   Tx1 = Tx2
2. Put Ty1, Ty2, Tx1, and Tx2 in terms of T1 and T2
   T1sinθ + T2cosθ = mg

3. Set T1 in terms of T2 and Substitute
    Because T1 = T2, this is possible. 
    Do  T1sinθ1 + T1sinθ2 = mg 
4. Solve for T1 
5. Go back and solve for T2
     T1 = (T2cosθ)/ cosθ

Question 14

X =

Y =

Answer 14

X = cos

Y = sin

Question 15

Inclined plane equations / reminders (4)

Answer 15

Fnet = mgsinθ - Fk 
Fk = μkFn 

Fnet = mgsinθ - μkmgcosθ

Ma = mgsinθ - μkmgcosθ

A = sinθ - μkgcosθ

Question 16

Tension problems equations / reminders (4)

Answer 16

Ty₁ + Ty₂ = mg

T₁sinθ + T₂sinθ = mg

Tx₁ = Tx₂

T₁cosθ = T₂cosθ (find T₁ and substitute for T₂)

Question 17

Force problem equations and reminders (6)

Answer 17

Fx₁ = Fx₂ 
Fx₁ = F₁cosθ
Fx₂ = F₂cosθ

Fnetx = F₁cosθ + F₂cosθ

Fnety = F₂sinθ + F₂sinθ

Above / below horizontal!

Question 18

How do concussions occur?

Answer 18

The brain “floats” around in the skull, it will remain in its current state of motion until it crashes into the skull. The bruising of the brain is the concussion.

Question 19

If a bug hits a car windshield, what are the forces exerted? Why is the car unaffected? What will happen to the cars acceleration at the time of impact? (3)

Answer 19

Bug and car exert equal forces

The windshield was made to withstand forces such as that

The acceleration will slight decelerate at the time of impact

Question 20

How is it possible for a little boy to pull a wagon across his yard? Use Newton’s third law to explain

Answer 20

The boys feet push against the ground in the x-axis direction and the friction between the two surfaces allows the ground to “return” a lot of that force due to Newton’s third law

Question 21

What are “Force pairs” and give an example.

Answer 21

Force pairs are action-reaction forces between two objects

Ex. Kicking a ball and you exert a force by your foot

The same force is exerted BY the ball ON your foot

Question 22

If similar boxes slide down a ramp at the same angle, but one box has a little extra weight on it, what box slides down the fastest?

Answer 22

They both slide down at the same rate because the masses cancel out in the solving of the equations, meaning the mass is irrelevant

Question 23

To prove that tanθ = μ (friction)… (6)

Answer 23

Fs = mgsinθ
μFn = mgsinθ
μmgcosθ = mgsinθ
μcosθ = sinθ
μ = sinθ/cosθ
μ = tanθ