1. Forces And Motion Flashcards
(24 cards)
Because of gravitational force…
Moons orbit …
Planets orbit…
Artificial satellites orbit…
Comets orbit…
Moons orbit planets
Planets orbit the sun
Artificial satellites orbit the earth
Comets orbit the sun
What is the equation for orbital speed?
Orbital speed= (2 x pi x orbital radius) / time period
What is the universe made up of?
What is a galaxy made up of?
Which galaxy is our solar system in?
The universe contains many galaxies.
A galaxy contains many stars, each star has a solar system.
Our solar system is in the Milky Way galaxy.
Describe the differences in the orbits of comets, moons, and planets
Planets orbit in circles
Comets and the Moon orbit in ovals (ellipses)
What is gravitational field strength?
How is it different on the moon than on earth? Why does it differ?
Gravitational field strength is how strongly something pulls an object towards it.
Earth has a stronger gravitational field strength than the moon. This is because the earth is bigger than the moon ( bigger planets than earth will have a stronger gravitational field strength )
describe elastic behaviour as the ability of a material to recover its original shape after the forces causing deformation have been removed.
Elastic behaviour is the way that when you stretch an object with this behaviour it will return to its origional shape after the forces stretching it stop stretching it.
E.g. when you stretch an elastic band and then let go it pings back to regain its original shape and size.
Note: if you stretch an elastic band too far it won’t go back. this is because it has reached its elastic limit which, beyond this point, means it looses its elastic behaviour.
How is the initial linear region of a force-extension graph associated with Hooke’s law?
What is Hooke’s law?
Hooke’s law: When an elastic object - such as a spring - is stretched, the increased length is called its extension. The extension of an elastic object is directly proportional to the force applied to it.
A force extension graph shows how much a material stretches for the force applied.
The initial linear region is the straight diagonal line showing a linear correlation between force and extension meaning that they increase at the same rate. This is Hooke’s law.
But at some point the graph will begin to curve, this is when an object reaches its elastic potential.
describe experiments to investigate how extension varies with applied force for helical springs, metal wires and rubber bands
The most common experiment:
- Attach a spring to a newton meter and measure its length
- Add a 50g weight and measure again
- continue to add another weight and take another measurement
- Do this up to 400g
by plotting a graph from the results from this you can see the extension increases with force; as each time a weight is added the spring gets longer.
What is a ‘moment’?
What is the ‘moment’ equation?
Complete: if a straight line is balanced, the clockwise and anti-clockwise moments will be …
An object turned around a pivot when force is applied is a moment.
Moment = force x distance(from pivot)
if a straight line is balanced, the clockwise and anti-clockwise moments will be the same.
What is Newton’s third law?
‘Each force has an equal and opposite force’ - two bodies interacting are both exerting a force on each other.
( when you swim you push back on the water, which pushes you forward)
What is the relationship between force, change in momentum, and time taken? (Equation)
Force=
Force = change in momentum / time taken
What is the equation which links mass, velocity, and momentum?
Momentum=
Momentum= mass x velocity
Use the idea of momentum to explain safety features:
What do crumple zones/air bags in cars do?
If the time taken for momentum to change is increased, the overall force felt is…(increased/decreased)
Crumple zones in cars increase the time it takes for the cars momentum to reach zero, meaning passengers feel less of the force.
If the time taken for momentum to change is increased, the overall force felt is decreased.
Which factors affect vehicle stopping distance?
The speed the car is travelling at
How heavy the car is
If the weather conditions are poor
How worn the brakes/tyres are
The condition of the driver (thinking distance) - drugs/tiredness
describe experiments to investigate the forces acting on falling objects such as sycamore seeds or parachutes
Dropping parachutes from a given height; this shows us that gravity is acting on them.
By increasing the size of the parachute and recording the results we can see that air resistance also has an effect on falling objects; plotting a graph should reveal that bigger surface area takes more time, from which we can infer that air resistance acts on the falling objects.
describe experiments to investigate the motion of everyday objects such as toy cars or tennis balls
You could plot the time it takes for a toy car to travel and then plot a distance time graph. Then repeat at different speeds and compare the different graphs.
Alternatively, you could use a ticker tape; this makes a mark every second on the tape. If you attach the car to the end of the tape, its speed will be recorded: distance/dots = speed. For example, if you has 50 dots on a meter tape then it traveled at an average speed of (1/50) 0.02 meters per second.
describe the forces acting on falling objects and explain why falling objects reach a terminal velocity
When first an object is falling it is accelerating- the force acting downward (gravity) is larger than the force acting upwards (air resistance.)
But when air resistance and gravity become equal the object will have reached its maximum speed; its terminal velocity. (All forces acting on the object are balanced)
The equation linking weight, mass, and gravity
Weight=
Weight = mass x gravity
Equation linking force, acceleration, and mass
Force=
Force = mass x acceleration
What is a vector quantity?
What is a scalar quantity?
A vector quantity has magnitude and a direction. (E.g. Velocity - speed with direction)
A scalar quantity just has a magnitude. (E.g. Speed)
Why is force a vector quantity?
Force has magnitude, it is measured in newtons but it acts in a direction.
E.g. 3N drag (the amount of force acting backwards)
describe the effects of forces between bodies such as changes in speed, shape or direction
Changes in speed-
When an object is stationary it has an equal force pushing down and up. The downward force being gravity and the upward force being the surface the object is on.
When an object is accelerating it has the upwards and downwards forces but it also has forwards and backwards forces (drag and friction). The forward force is larger than the backward force when an object is accelerating.
When an object is going at a constant speed it has downward and upward forces as well as forward and backward forces. The forward and backward forces are equal, so the speed doesn’t change even though the object is moving.
When an object is decelerating it has the equal upward and downward forces as well as forward and backward forces, but the backward force is larger than the forward one, slowing the object down.
Changes in shape-
changes in shape affect momentum. Force= change in momentum/ time taken. An example of this is crumple zones in car decrease the force on the passengers.
Changes in direction-
Which ever direction the force is greatest in will be the direction the object travels in.
What equation links acceleration, velocity, and time?
Acceleration =
Acceleration = change in velocity / time taken
Units : Frequency= Force= Power= Current= Temperature= Work/Energy = Pressure = Resistance =
Frequency= hertz Force= newtons Power= watts Current= ampere (amps) Temperature= kelvin Work/Energy = joules Pressure = pascals Resistance= Ohms
