Motion

What is speed

The rate at which an object moves a certain distance

What is displacement

The overall change in position of an object in a specific direction

What is velocity

Rate of change of displacement or speed with direction

What is acceleration

The rate of change of velocity

What is the average speed of an object during a trip

The total distance travelled divided by the total time it took

What is instantaneous speed

The speed of an object at any specific moment

How can instantaneous speed/velocity be found

By drawing a tangent to the displacement time graph at the specific time and calculating the gradient

What does a displacement time graph show

How far an object has moved from its starting point and the time it took to move that distance

Describe a displacement time graph

Flat line= stationary, straight sloping line= constant speed/velocity, curve= acceleration/deceleration, gradient= velocity

What does a velocity time graph show

How quickly an object is travelling against time

Describe a velocity-time graph

Flat line= constant velocity, straight sloping line= constant acceleration, curve= variable acceleration, gradient= acceleration, area under graph= displacement

What is uniform acceleration

Where the acceleration of an object is constant

What is the difference between a scalar and a vector quantity

A vector is a quantity that has both magnitude and direction, while a scalar only has magnitude

What are the steps to adding vectors graphically

1) draw each vector accurately to scale

2) arrange the vectors tip to tail in sequence

3) measure the resultant vector from the start of the first vector to the tip of the last vector

Given a resultant vector at an angle how do you calculate the horizontal component

H = (magnitude of resultant vector) cos0

Given a resultant vector at an angle how do you calculate the vertical component

V = (magnitude of resultant vector) sin0

What do free body force diagrams show

All the forces acting on an object

What are the key features of a free body force diagram

Object is isolated from its environment, all force vectors are labelled and drawn, the relative magnitude and direction of each force are shown

When is an object in equilibrium

When the net force acting on it is zero, resulting in no acceleration

When is equilibrium achieved for two forces

The forces have equal magnitudes and act in opposite directions

When is equilibrium achieved for multiple forces

When the sum of all vector forces equals zero

What is Newton’s first law

An object will remain at rest or in uniform motion in a straight line unless acted upon by a resultant force

What is Newton’s second law

The acceleration of an object is directly proportional to the resultant force experienced by the object given that mass is constant

What is Newton’s third law

When body A exerts a force on body B, body B exerts an equal and opposite force back onto body A

How can Newton’s second law be expressed

F =ma

What is friction

A force that opposes the movement between to surfaces in contact

What two forms does friction come in

Contact- between solid surfaces

Drag- between a solid object and a fluid (water, air)

What are the characteristics of drag

Increases as the objects speed increases, affected by the thickness of fluid and shape and size of the object

When does terminal velocity occur

When an objects driving force and the opposing drag force balance each other out resulting in no resultant force and so no acceleration so the object travels at a constant velocity

Explain the three stages of terminal velocity

The object accelerates from a standstill due to a constant driving force, as the object speeds up, drag force increases slowing the acceleration, the driving force and drag force become equal leading to a constant velocity known as terminal velocity

What is a projectile

Any object with an initial velocity that then moves freely under gravity

What are key points about projectiles

Horizontal and vertical components of a projectiles motion are independent, the horizontal velocity remains constant while the vertical velocity changes due to gravity (this causes the curved path), the vertical component of velocity is 0m/s at the highest point

Forces and velocities can…

…act in any direction

How must a motion be resolved

Into horizontal and vertical vectors using trigonometry

What does the initial velocity determine

The time of flight and maximum height

What is a moment

The turning effect generated when a force is applied at a distance from a pivot point

What is a moments strength determined by

The magnitude of the force, the perpendicular distance from the pivot point

What does the principle of moment states for an object to remain in equilibrium

The total clockwise moments around any point must be equal to the total anticlockwise moments

What happens if the moments are not balanced

The resultant moment will cause the object to rotate

Explain what a torque produced by a couple is

A couple consists of two equal and opposite forces acting parallel to each other but separated by distance. This setup creates a torque inducing rotation

What is momentum

A vector quantity defined as the product of mass and velocity

What is the conservation of momentum

That momentum is always conserved in a closed system without external forces. This means total momentum of all objects before is equal to their total momentum after the interaction

What are collisions categorised as

Elastic- where kinetics