Level Four Physics - Space and Dynamics Flashcards
What is Speed?
Speed is the distance travelled by an object in one second.
What is speed measured in?
Speed is typically measured in meters per second, ms-1
What are the two types of speed?
- Average Speed
- Instantaneous Speed
What is average speed?
The average for the whole journey (total distance divided by total time)
What is instantaneous speed?
The speed of an object at one particular point in the journey.
What is the formula to calculate speed?
v=d/t
What is acceleration?
Acceleration is how much it’s speed changes in one second.
What is acceleration measured in?
Meters per second, per second (ms-2)
How can acceleration be calculated?
By dividing the change in speed by the time taken.
formula for acceleration
a=v-u/t
What can speed-time graphs help do?
Speed time graphs can help describe the motion of an object.
Time is on the x-axis.
A positive gradient means increasing speed.
No gradient means constant speed.
A negative gradient means decreasing speed.
What can forces change?
- The speed of an object’
- The shape of an object
- The direction of motion of an object.
What is used to measure forces?
A Newton balance
How does a Newton Balance work?
When a force is applied to the balance the spring becomes longer. The increase in length is directly proportional to the force applied.
What is weight?
Weight of an object is the force on it due to the Earth’s gravitational pull
What is weight measured in?
Weight is measured in Newtons as it is a force.
What is mass?
Mass is the amount of matter that makes up an object.
What is mass measured in?
Mass is measured in kilograms.
What is gravitational field strength?
Gravitational field strength of a planet is the weight per unit mass of an object on that planet.
What is the symbol for gravitational field strength?
g
What is gravitational field strength measured in?
Newtons per kilogram (N/kg)
What is the relationship between weight, mass and gravitational field strength?
W=mg
What is friction?
Friction is a force that opposes the motion of an object.
It acts in the OPPOSITE direction to the motion.
What does friction acts between?
Friction acts between two surfaces in contact. When one surface moves over another, the force of friction acts between the surfaces and the size of the force depends on the surface?
What type of surface will give the most friction - a rough surface or a smooth surface?
A rough surface.
What is another name for air resistance?
Drag
What is air resistance or drag?
Air resistance or drag is the force of friction due to the object’s motion through the air.
What are the two main factors that air resistance or drag depend on?
- The shape and size of an object
- The speed of the object
What causes air resistance to increase?
Increasing speed of movoment
3 situations where friction is wanted/increased
- Applying the brakes of the car.
- Opening a parachute
- Wearing rubber soled shoes for rock climbing.
3 situations where friction is unwanted/decreased
- Making cars streamlined
- Oiling moving parts in a car engine
- Using an air cushion on an ‘air hockey’ table.
What are balanced forces?
When equal forces act in opposite directions
What are balanced forces equivalent to?
Balanced forces are equivalent to no forces at all
What are balanced forces equivalent to?
Balanced forces are equivalent to no forces at all
Newton’s First Law of Motion
When balanced forces (or no forces) act on an object it remains at rest or continues to move at a steady speed in a straight line.
What would happen if a passenger was not wearing a seatbelt and the car crashes?
The passenger would continue to move forward at constant speed (Newton’s first law) until they are stopped by something.
What do seatbelts do?
Seatbelts apply a backwards force to stop the passenger continuing to move forward at constant speed.
What happens when unbalanced forces act on an object?
The object changes speed or direction
What happens when the force stays constant and mass increases ?
Acceleration decreases
What happens when the mass stays constant and force increases ?
Acceleration increases.
Newton’s Second Law
Force= mass x acceleration
F=ma
What is a light year?
A light year is the distance travelled by light in one year.
What distance is a light year?
9.46 x 10^15 m
Newton’s Third Law of Motion
‘Every Action has an Equal and Opposite Reaction’
Def. of Universe
The Universe consists of many galaxies separated by empty space.
What is a galaxy?
A galaxy is a large cluster of stars.
What is a star?
A star is a large ball of matter that that is undergoing nuclear fusion and emitting light.
What is a solar system?
A solar system consists of a central star orbited by planets.
What is a planet?
A large ball of matter that orbits a star. They do not emit light themselves.
What is a moon?
A moon is a lump of a matter that orbits a planet
How many minutes does it take light to reach Earth from the Sun?
It takes 8 minutes.
How many years does it take light from Proxima Centauri (Nearest Star) to reach Earth?
4.3 years
How many years does it take light from the Edge of the Galaxy to reach Earth?
100,000 years
When a spacecraft re-enters the Earth’s atmosphere it experiences what with the atmosphere?
Friction
When a spacecraft re-enters the Earth’s atmosphere kinetic energy gets changed into?
Heat energy
This means that spacecraft have to be covered with hear shielding to prevent them from burning up on re-entry.
What is projectile motion?
When an object is projected in a gravitational field it will follow a curved path.
What forces are acting on an object whilst its in projectile motion?
1 - the force of gravity (weight) acting vertically downward
The affect of gravity acting constantly vertically downwards results in -
constant downward acceleration.
Whereas there are no horizontal forces so the object moves with
constant horizontal speed
Satellite motion is an extension of
projectile motion
A satellite is constantly what?
Accelerating towards the Earth like any other projectile, however the satellite is moving so fast taht the Earth curves away from it as quickly as it falls.
What does this mean for the satellite?
It never reaches the Earth ut continues to move in orbit
When an object is in freefall it appears to be what
weightless
Things appear to be weightless because
the spacecraft and the astronauts are falling towards the Earth at the same rate.
