Flashcards in Physics - Forces And Newtons Laws Deck (24)

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## Newton's first law

### 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

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## Mass

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The measure of the amount of matter in an object

Measured in kilograms

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## Inertia

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

More mass = more inertia

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## Microwelds

### Occur when two bumpy surfaces are rubbed up against each other

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## Newton's second law?

### F = m x a

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## Weight (force) =

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Mass x gravity (earth)

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

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## Newton's third law

### For every action there is an equal and opposite reaction

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## Fn =

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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

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## How to find friction force??

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Ff = μFn

Ff = friction force (N)

μ = coefficient of friction

Fn = normal force (N)

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## Friction

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

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## An object at rest has what kind of acceleration?

### Acceleration is 0

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## If acceleration is zero...

### Net force is equal to zero

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## Tension

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

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## Steps to tension problems (5)

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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

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##
X =

Y =

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X = cos

Y = sin

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## Inclined plane equations / reminders (4)

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Fnet = mgsinθ - Fk

Fk = μkFn

Fnet = mgsinθ - μkmgcosθ

Ma = mgsinθ - μkmgcosθ

A = sinθ - μkgcosθ

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## Tension problems equations / reminders (4)

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Ty₁ + Ty₂ = mg

T₁sinθ + T₂sinθ = mg

Tx₁ = Tx₂

T₁cosθ = T₂cosθ (find T₁ and substitute for T₂)

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## Force problem equations and reminders (6)

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Fx₁ = Fx₂

Fx₁ = F₁cosθ

Fx₂ = F₂cosθ

Fnetx = F₁cosθ + F₂cosθ

Fnety = F₂sinθ + F₂sinθ

Above / below horizontal!

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## How do concussions occur?

### 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.

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## 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)

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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

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

### 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

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## What are "Force pairs" and give an example.

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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

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## 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?

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

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