Motion And Energy Flashcards
(38 cards)
Speed
Speed is a measure of how fast something moves.
The rate of change of distance
Distance
A measurement of how far apart objects are
Displacement
A measurement of the change in position of a moving person. A straight line connecting the start and end point is specified in terms of length and direction
Acceleration
Rate of change of velocity
Units to measure speed
Metres per second , kilometres per hour
Distance travelled in a certain amount of time
To convert km to m, divide by 3.6
To convert m to km, times by 3.6
Force
Force are pushes, pulls or twists. A force can make an object start moving, speed up, slow down, change direction or shape. Sometimes forces are balanced so you can’t tell there is a force acting upon something.
Newton’s first law
An object at rest will remain this way unless it is acted upon by a force.
An object that is moving will continue to move at the same speed and in the same direction unless an unbalanced force acts upon it.
Aka a force is needed to get something moving, change direction or speed
Inertia
The tendency of an object to resist any changes in its motion. The larger the mass of an object, the greater its inertia and the harder it is to change its motion.
Inertia cars and buses examples
It takes more fuel and force to move a heavy truck then a small car because of its inertia.
If you are travelling in a car at 60km, you are travelling at the same speed because you are inside the car. When it comes to a stop because the force of the breaks stops the car, your body continues to travel at 60km/h because no force has been acted up it to stop (unless there are seat belts or airbags)
Safety features in modern cars
Air bags inflate when the car collides with a solid object above the speed of 18km/h. Reducing the force on a passenger in a collision. Seat belts restrain the body so that you come to a stop with the car
Newton’s second law
An object will accelerate in the direction of an unbalanced force acting upon in it. The size of this acceleration depends upon the mass of the object and the size of the force acting.
A larger force is needed to accelerate a heavy load than a lighter load
A larger force is required to make something accelerate at a faster rate
Force formula
F = m x a
Mass formula
M = F
—
A
Acceleration formula
A = F Or A = v-u
— ——
M T
Newton’s third law
For every action force there is an equal and opposite reaction force
Action force: a nail is hit by a hammer
Reaction: the nail exerts an equal force back on the hammer as the hammer hits the nail down
Action force: a tennis ball is hit by a racquet
Reaction: the racquet applies a force on the ball and the ball accelerates forwards. The ball also exerts a force back onto the racquet
Action force: a sprinter pushes back on the starting blocks as a race begins
The starting blocks push forward on the sprinter
Action force: a book resting on a table exerts its weight force onto the table
The table exerts an equal support force upwards on the book
Action force: an octopus squirts water out as jets through a tube just below its head
These water jets push back on the octopus, propelling it in the opposite direction
Action force: you stand on a skateboard and push against the wall
The wall pushes back on you with equal force and you move away
Speed formula
V = d
—
T
Kinetic energy formula
E = 1/2 mv2
Gravitational potential energy formula
E(p) = mgh (g=9.8)
