Forces and motion

what is the stopping distance of a vehicle made up of?

the thinking distance + braking distance

what factors affect vehicle braking distance?

speed, mass, road condition and reaction time

what influences thinking distance?

tiredness, intake of alcohol/drugs, distractions, age

why do falling objects reach a terminal velocity?

object’s weight causes it to accelerate downwards.

As speed increases, the air resistance acting upwards on it also increases.

air resistance increases until it is equal to the object's weight.

resultant force is zero/

what is Hooke’s Law (spring force)?

The force applied to a spring is directly proportional to the distance it is stretched.

What is the spring constant?

A measure of the spring’s stiffness- a higher value means a stiffer spring

Elastic behaviour

a material's ability to return to its original shape/ size after a deforming force is removed

elastic limit

the maximum stress a material can withstand without permanent deformation

inelastic deformation

A permanent change in shape or size that remains after the force is removed. 

what is the equation for force, change in momentum and time taken?

f= m(v-u)/t

what is newton’s third law?

When one object exerts a force on another object it will exert a force that is equal in magnitude and opposite in direction

what is the centre of gravity?

the point where the object's entire weight is concentrated

what is the centre of mass?

the average position of all the mass in an object

what is the principle of moments?

for an object to be in equilibrium, clockwise moments = anticlockwise moments around a pivot point

what is newton’s second law?

the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass

what is momentum recoil?

The backward movement of an object is due to the conservation of momentum when another part of the system is propelled forward

momentum definition

a measure of how much mass is in motion

what is the difference between vector and scalar quantities?

scalar quantity only has a magnitude

vector quantity has both magnitude and direction

what are the typical methods uses to measure the motion of moving objects?

light gates

ticker tape

stopwatch + ruler

what are the effects of force on an object?

change in speed

change in direction

change in shape

what are the types of forces?

gravitational

electrostatic

magnetic

friction

normal contact force

tension

upthrust

air resistance

what are the contact forces?

friction, normal force, tension, air resistance, upthrust

what are the non-contact forces?

gravity, electrostatic, magnetic

how are momentum and seatbelt safety features related?

• Stretch slightly during a collisions

• increase impact time

• same momentum change

• Reducing the force acting on the passenger

how are momentum and airbag safety features related?

• Inflate and cushion the passenger on impact

• increases impact time

• same momentum change

• Spreads the force over a larger area

how are momentum and crumple zone safety features related?

• The front/rear of a car is designed to deform (crumple) on impact

• increase impact time

• same momentum change

• Reducing the force on the passenger