Unit 3- Dynamics and Space Flashcards
What is a vector quantity?
Specified by magnitude and direction
Vector quantities include…
Velocity, weight, acceleration, displacement, force
When do you add vectors?
If they are in the same direction
When do you subtract vectors?
If they are in the opposite direction
What is the resultant displacement?
The sum of two displacements at right angles to one another
Speed time graphs:
Constant acceleration is shown by…
A diagonal line going upwards
Speed time graphs:
Constant deceleration is shown by…
A diagonal line going downwards
Speed time graphs:
Constant speed is shown by…
A straight line
How can the distance travelled be calculated on a speed time graph?
By calculating the area of each section underneath it (divide into triangles and rectangles, then find the area, then add them together)
Name a method of measuring instantaneous speed
Using a speedometer in a car, or a computer connected to light gates
How can light gates be used to measure speed?
Instantaneous speed= length of card/ time beam is blocked
What is the definition of Acceleration
The change in velocity per unit time
Using light gates to measure acceleration
You must know the
initial velocity,
the final velocity,
Time taken to pass from one light gate to another
What is Newton’s first law?
An object at rest will remain at rest unless acted upon by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
What is Newton’s second law?
If an object is acted on by an unbalanced force it will accelerate. The amount of acceleration increases as the force increases. However if you apply the same force to a larger mass the acceleration will be less
When does work take place?
When an object is moved by a force, the force transferring energy to the object
Eg/ if an archer pulls back a string on a bow and arrow the work done stretching the sting will be transferred to the arrow when it is fired
What is the definition of gravitational field strength?
The force per unit mass
What is Newton’s third law?
For every action force there is an equal and opposite reaction force
Describe terminal velocity
When a skydiver jumps out of a plane they accelerate downwards due to the force of gravity. As their speed increases so does the force of friction (due to air resistance) eventually the weight and friction become equal.
There are now no unbalanced forces acting on them, so they continue downwards at a steady speed. They have reached their terminal velocity
What is a projectile?
An object which has a forwards speed at the same time as it as falling freely through the air
Describe the vertical motion of a projectile (in terms of a graph)
A diagonal line doing upwards
Describe the horozontal motion of a projectile (in terms of a graph)
Straight line
What is a satellite?
Like a projectile which is falling towards the earths surface at the same rate as the earths surface is curving away from the satellite. The satellite at this point is said to be in orbit
Describe a geostationary satellite
They orbit the Earth once every 24 hours
They always remain in the same position above the earths surface
They are mostly used for communications and weather observation
What are the benefits of space exploration?
Communication- uses satellites
Jobs- many people employed in the industry
Spin off technologies- bar codes, non stick pans
Mapping- using satellites can improve land use
What are the risks of space exploration?
Danger to life- several astronauts have lost their lives in missions
Cost- the money could be spend elsewhere, the budget is high
What are the dangers on re-entry of the atmosphere?
If the spacecraft hits the atmosphere at the wrong angle it can bounce back into space
The atmosphere creates friction, and so heat. The space craft may face overheating
What is the definition of latent heat of fusion?
The energy added or removed from 1 kilogram of substance to change it from solid to liquid or liquid to solid
What is the definition of a light year?
The distance that light will travel in one year
How far is the sun from the earth?
8.5 minutes
How far is the sun to the nearest star?
4.3 light years
What is the diameter of the Milky Way?
120,000 light years
What is a scalar quantity?
Specified by magnitude alone
