P2.1 Flashcards
What is an example of magnetism
A metal car being attracted to a magnet; the magnet is attracted to the car with equal and opposite force
What is an example of gravity
A ball being attracted for the planet; the planet is attracted to the ball with an equal and opposite force but the ball has a much smaller mass so it’s the ball that moves
What is equal and opposite force
The same force acting on different objects
What is a resultant force
The sum of different forces acting on the same object
What do we call it if the resultant force is zero
What do we call it if the resultant force is not zero
We say that the forces are balanced
We say that the forces are unbalanced
What happens of the resultant force is zero
If the object is not moving it stays where it is
If the object is moving it keep moving at the same speed in the same direction
What happens if the resultant force is not zero
The object will accelerate in the direction of the resultant force
Object will accelerate in the direction of the resultant force, making it slow down, speed up or change direction
What does the acceleration of an object depend on
The size of the unbalanced force- the bigger the force the greater the acceleration
The mass of the object- the bigger the mass, the smaller the acceleration
What is the formula for resultant force
Resultant force (N) = Mass (kg) X Acceleration (m/s2)
What is the formula for speed
Speed (m/s) = Distance (m)
Time (s)
What is velocity
Speed with a direction
What is acceleration
The rate at which its velocity changes
What is the formula for acceleration
Acceleration (m/s2) =
Velocity change (m/s)
Time taken for change (s)What needs to happen for a car to stop
It needs to lose all its kinetic energy
What happens when the breaks are applied
They work to transfer the kinetic energy of the vehicle into heat energy in the brakes. The breaks therefore increase temperature
What does the stopping distance of a vehicle depend on
Thinking distance
Braking distance
What’s thinking distance
The distance travelled by the vehicle from the point when the driver sees that he needs the stop to when he actually applies the breaks
What’s breaking distance
The distance travelled by the vehicle from the point when the driver applies the breaks to where the vehicle actually stops
Factors affecting thinking distance
Tiredness
Influence of drugs or alcohol
Being distracted e.g. By mobile phone or passengers
Factors affecting breaking distance
Adverse weather conditions e.g. Wet or icy roads
Poor conditions of vehicle e.g, brakes and tyres
What two forces do falling objects experience
Downwards force of weight
The upwards force of air resistance
What are the different stages of skydiving
Initially he accelerates because of the force due to gravity. He then experiences the air resistance but this is not as great as his weight so he continues to accelerate. As his speed increases so does the air resistance until eventually R is equal to W. This speed is calling terminal velocity. When the parachute opens the upwards force of R is now bigger than W. This decreases his speed and as his speed decreases so does R. Eventually R decreases till its equal to W. Falls at steady speed.
Formula for weight
Weight (N) = Mass (Kg) X Gravitational field strength (N/Kg)
What do people consider when designing vehicles
What are racing cars designed like
To increase top speed and be more fuel efficient vehicles are designed to be streamline so as to reduce drag
They have a powerful engine to give a big driving force while being lightweight and very streamline. This combination means that they accelerate quickly and have to be going very fast before the drag force equals the driving force
What is the force directly proportional to when you stretch an elastic object
The extension (the amount it is stretched by)
What is it called when the extension exceeds a certain value
What happens
The limit of proportionality
The force and extension stop being directly proportional
What is the formula for force
Force (N) = Spring constant (N/m) X Extension (m)
