Speed in a given direction rate of change of displacement

Section 4.1 - Mechanics Flashcards by ROWAN Gomanee

Define vector

A quantity with both magnitude and direction

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Define scalar

A quantitiy that has no direction

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What are 5 examples of a Scalar?

Distance,Density, Temperature,Energy,Speed

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What are 5 examples of a vector quantity?

Force,Displacement,Acceleration,Velocity,
Momentum

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Define displacment

Distance in a given direction

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Define Velocity

Speed in a given direction
rate of change of displacement

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Define acceleration

Rate of change of velocity

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What is it called when the resultant of all the forces on an object equals 0?

Equillibrium

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Define a moment

The force * perpendicular distance from the line of action of the force to the pivot point

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What is the principle of moments?

The sum of the clockwise moments is equal to the sum of the anti-clockwise moments

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Define centre of mass

The point through which a single force on the body has no turning effect.

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What is the moment of a couple?

Moment of a couple = Force * Perpendicular distance between the lines of action of forces

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What must be true for two forces to be considered a couple?

Acting around a pivot
Equal and opposite forces but not along the same line

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What is stable equilibrium?

If a body in stable equillibrium is displaced then released it will return to its equilibrium position

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What is unstable equilibrium?

When a body in unstable equilibrium is displaced it will not return to its equilibrium postion

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What is the gradient of a displacement/ time graph?

Velocity

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What does a x vs t graph look like at consant velocity

Linear

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What is the gradient of a velocity / time graph

Acceleration

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What is the formula for constant acceleration

a = v - u
—–
t

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What are the SUVAT equations?

V = u +at
S = ut + 0.5 *at²
S = vt - 0.5 *at²
V² = u² + 2as
S= 0.5(u+v)t

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What is the area under a V/t graph

Displacement

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What is the area under an a/t graph?

velocity

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Define free fall

An object that is accelerating due to gravity

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What is terminal velocity?

Terminal speed occurs where the frictional forces acting on an object and driving forces are equal, therefore there is no resultant force and so no acceleration so the object travels at a constant speed

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How does air resistance affect projectile motion?

Greatest hieght and distance are both reduced

What is newtons 1st law?

An object will remain at rest or constant velocity unless acted upon by an external force

What is newtons 2nd law?

The acceleration of an object is proportional to the resultant force experienced by the object

What is newtons 3rd law?

Every action has an equal and opposite action that is : * equal in magnitude * the same type of force * in the opposite direction * acting on a diffent object

What is a free body diagram?

a diagram which shows all the forces that act on an object

What is stopping distance?

Thinking distance + braking distance

What is braking distance?

The distance travelled by a car from the moment the brakes are applied

What is thinking distance?

The distance travelled in the time it takes the driver to react

What is momentum?

p = mass * velocity

What is the unit for momentum?

kgm(s^-1)

Extended version of newtons second law?

Force is proportoinal to the rate of change of momentum

What is impulse?

Ft = Δ(mv)

What is the area under a force time graph?

The impulse

What is the change of momemntum when an object rebounds normally?

-2mu

What is the change of momentum when an object does not rebound normally?

-2mu.cosθ

What is the principle of conservation of momentum?

total momentum remains constant provided no external reultant force acts on the system

What is the equation for the force on object A in terms of mass and velocities?

F = (mₐuₐ - mₐvₐ)/t

What is the equation for the forces on two objects colliding?

Fₐ = -Fᵦ

What is the eqaution for total final momentum?

mₐvₐ+mᵦvᵦ =mₐuₐ + mᵦuᵦ

What is the velocity of the two objetcts if they stick together?

They have the same velocity

What is an elastic collison?

* A collision in which there is no loss of kinetic energy. * Energy and momentum is conserved

What is an inelastic collision?

* The colliding objects have less kinetic energy after the collision than before * Only momentum is conserved

Is an explosion an elastic or inelastic collision?

inelastic

List 4 stores of energy

* GPE * Kinetic * thermal * Elastic

List 3 ways of tranfering energy

* Radiaiton * Electrically * mechanically

What is a joule?

The energy needed to raise 1N through a vertical height of 1m

What is the principle of conservation of energy?

Energy cannot be created or destroyed

What is work done?

* W = force * distance moved in the direction of the force * W = F.s.Cosθ

What is the area under a F vs d graph

Work done

What is kinetic energy?

The energy due to an objects motion

Formula for kinetic energy?

Ek = 0.5*mv²

What is potential energy?

The energy due to an objects positon

What is the formula for GPE

GPE = mgΔh

What is power?

The rate of transfer of energy

What is the formula for power in terms of force?

P = fv

Formula for efficency?

e = useful energy out ====== total energy in

Describe and Explain Uniformly accelerated motion

* Constant acceleration * Resultant force = m.a where m is constant * SUVAT * Each dimension has separate equations * S vs t graph is a quadratic graph; S = ut + 0.5at² * v vs t graph is a linear graph; gradient is a * a vs t graph horizontal line

Describe and Explain Newtons second law of motion

* RF = ma; Resultant force is the product of mass and acceleration * RF = (mv - mu)/t = ΔP/t * Force is proportional to the rate of change of momentum

Describe and Explain Projectile motion

* Parabolic trajectory * sᵪ = uᵪ * t * sᵧ = uᵧt + 0.5* gt² * vᵧ = uᵧ + at * vᵪ = uᵪ * aᵪ = 0; constant horizontal velocity * aᵧ = g = -9.81; constant vertical acceleration

Describe and explain Hookes' law

* Force applied by a spring is in the opposite direction to the extension F = k.e E = 0.5 * Fe = 0.5ke²

Describe and explain Newtons 3rd law of motion

* Forces occur in pairs * Equal in magnitude * Same type of Force * oppostie in direction * act on different objects

Describe and explain Conservation of Linear momentum

* P =mv * Sum of momentum before = sum of momentum after * momentum is conserved in a particular direction * No external forces act on the system * F₁ = (m₁v₁ - m₁u₁)/t 2nd law F₂ = (m₂v₂ - m₂u₂)/t 2nd law F₁ = -F₂