Section 2 Flashcards
What do free body force diagrams show
A single body on its own with all the forces that act on the body but not the forces it exerts on the world
The greater the mass the greater its _________ to a change in _________
resistance
velocity
Centre of mass
The single point that is considered the weight is concentrated
Centre of mass experiment
Hang the object from a point
draw vertical line down from point of suspension with plumb line
Repeat from different point
Stable objects
Low centre of mass
Wide base
Unstable objects
High centre of mass
Small base
When something topples
Centre of mass falls outside its base area
Friction
Force that opposes motion
What does friction convert
Kinetic energy into heat
When will terminal velocity be reached?
A driving force that stays the same all the time
A drag force that increases with speed
4 stages of skydiving
stage one
Skydiver will jump and only his weight acts
As he falls, air resistance increases
4 stages of skydiving
stage two
The skydivers air resistance will equal his weight and he travels at terminal velocity
4 stages of skydiving
stage three
parachute opens and air resistance is larger than weight so he slows down
4 stages of skydiving
stage four
He slows down until his speed has dropped enough for his air resistance to equal his weight so he hits terminal velocity again
How does liquid effect terminal velocity
it will be lower because thicker liquids produce more drag
How does the shape effect terminal velocity
Drag will be greater with less streamlined shapes
How does mass effect terminal velocity
reach terminal velocity faster because a greater drag force is needed to balance the extra weight
Pressure
force per unit area
Pressure units
Pa
Nm-2
Why do bodies experience upthrust
the top and bottom of the submerged object is at different depths so there’s a difference in pressure which causes an overall force known as upthrust
Archimedes principle
When a body is submerged in water, it experiences upthrust equal to the weight of the fluid it has displaced
principle of moments
for a body to be in equilibrium, the sum of the clockwise moments must equal the sum of the anticlockwise moments about the same point
A couple
A pair of forces of equal size, parallel to each other but in opposite directions with distance between them
What does a couple produce
A turning moment called a torque
