Chapter 8 Flashcards
what is displacement?
measures the distance and direction between a start and end point in a straight line
what is a vector?
a physical quantity with a direction and size (magnitude)
what is a scalar?
a physical quantity with just size (magnitude)
difference between speed and velocity
speed is a scalar - it just has a size
velocity is a vector - it has size and direction
typical speed of a person walking
1.5 m/s
typical speed of a person running
3 m/s
typical speed of a person cycling
6 m/s
typical speed of a car
25 m/s
typical speed of a train
55 m/s
typical speed of a plane
250 m/s
what is distance?
how far an object has moved
what does the direction of an arrow represent?
the direction of the vector quantity
what does the length of the arrow represent?
the magnitude of the vector quantity
what is a force?
a push or pull on an object because of its interaction with another object
what is a contact force?
when two objects must touch eachother to interact
Newton’s Third Law states:
when two objects interact with eachother, they exert equal and opposite forces on eachother
what is the driving force on a car?
the force that makes it move
what is force measured in?
Newtons (N)
what is a resultant force?
a single force that has the same effect on the object as all the forces combined
Newton’s First Law states:
if the forces acting on an object are balanced, the resultant force is 0
if the object is at rest, it stays stationery
if the object is moving, it keeps moving in the same direction with the same speed
if an object i acted on by two unequal forces, the resultant force:
is equal to the difference between the two
is in the direction of the larger force
what is a free-body force diagram?
it shows all the forces acting on an object without anything else being shown
How to increase the moment? 2
Increasing the size of the force
increasing the distance from the pivot
What is a moment?
The turning effect of a force
How to get the maximum moment?
The force needs to be applied perpendicular to the spanner
What is the load?
The weight of the object
What is the effort?
The force we apply
What is a force multiplier?
The effort we apply lifts a much bigger load
Equation for moment
force x perpendicular distance from pivot
How do bottle openers work?
The force you apply is further from the pivot than the edge of the cap. So, it acts as a force multiplier and we can lift the cap
Why are racing cars so low to the ground?
So they don’t overturn when they go round corners
What is the centre of mass of an object?
The point at which its mass can be thought of as being concentrated
When will a hanging object stop moving?
When its centre of mass is directly below the point of suspension
How to find the centre of mass of a flat object?
Draw on the lines of symmetry
It is where these lines cross
What is the principle of moments?
For an object that is not turning, the sum of all the clockwise moments about a point = the sum of all the anticlockwise moments about a point
How to draw a parallelogram of forces?
Draw the forces to scale as adjacent sides of a parellelogram
How to draw a scale diagram?
Work out the different forces acting on an object and the direction
Decide on and write down a scale
Draw suitable arrows to fit
What conditions must be present for an object to be in equilibrium? 2
No resultant force
No turning effect on the object
How to resolve a force?
SEE FLASHCARDS
How do gears work?
SEE FLASHCARDS?
Why would a ship being pulled by tugboats move at a constant velocity?
The combined tug of the boats is equal to the drag force so it doesn’t accelerate but travels at a constant speed
