P5 Flashcards
What is Work done?
The amount of energy transferred to an object by an external force when it is moved over a certain distance
What is the equation for work done?
Work done (S) = force (N) x distance(M)
What happens when a car breaks?
Break presses wheel, Force of friction is acting on break and wheel, Kinetic energy of car. Transfers to thermal energy, Temperature of break increase, car slows
What happens to elastic materials when we take away the forces acting on them
They return to the original length and shape
What is inelastic deformation?
Changes in shape or length in inelastic materials (does not change back)
What equation links force spring constant and extension?
Force (N) = spring constant (n/m)x extension(m)
What does distance tell us?
How far and object moves (not direction) is a scalar quantity
What does displacement tell us?
The distance that an object moves in a straight line from the start to the finish (vector)
What equation links, speed and time and distance?
Speed (m) = distance(m)/time (s)
What is the typical walking running and cycling speeds
Walking 1.5m/s
Running 3m/s
Cycling 6m/s
What is the velocity of an object?
The speed in a given direction
What is the velocity of an object at a constant speed travelling in a circle?
Velocity is constantly changing
How do you find the gradient of a distance time graph?
Gradient=distance travelled/time taken
What does acceleration tell us?
Change in velocity over a given time
What is the equation for acceleration ?
Acceleration (m/S(2)= Change in velocity (m/s)/ time(s)
What is the acceleration of an object falling towards the Earth?
9.8 m/s. Squared
What is terminal velocity?
The maximum speed achieved by an object freely falling through a gas or liquids
Why do some objects which fall experience a lower terminal velocity?
Experience more friction due to shape
What is Newton’s first law of motion?
-an object remains in the same state of motion unless a resultant force acts on it.
-If the resultant force on an object is zero this means:
a stationary object stays stationary
What is Newton second law of motion?
The acceleration of an object is proportional to the resultant force acting on an object and inversely proportional to the mass
What’s the equation for force
Force(N) = mass(kg)x acceleration(m/s squared)
What is inertia?
The tendency of an object to continue in its state of rest, or in uniform motion unless acted upon by an external force
What is inertial Mass?
The inertial mass is a measure of how difficult it is to change the velocity of an object
What is Newton’s third law of motion?
Whenever two objects interact, the exert equal and opposite forces
What is stopping distance?
The total distance travelled from when the driver first spots the obstruction, and to where the car stops
What is thinking distance?
The distance travelled by the car during the drivers reaction time
What is breaking distance?
The breaking distance is the distance, the car travels from when the driver applies the brakes to when the car stops
How can we measure reaction time?
One person holds a ruler and volunteer places fingers on either side of the bottom, Ruler is dropped volunteer catches, The further the ruler drops the longer the reaction time, Look up the distance in reaction time converter
What factors influence thinking distance?
Tiredness, alcohol, drugs and distractions
What Factors influence, breaking distance
Wet or icy conditions, less friction
Car has worn breaks, less friction
Worn brakes
Equation links, kinetic, energy, mass and velocity
Kinetic energy = 1/2 mass x velocity
What happens during breaking?
Brake pad presses wheel,friction acts between brake and wheel,KE of car is converted to TE in brakes,temperature of brakes increase,car slows as it loses KE
What are the dangers of applying a very large braking force if a car is going fast
Car decelerates rapidly. A large amount of kinetic energy is transferred to thermal energy in the brakes causing the brakes to overheat,driver could lose control .
What is momentum of a non-moving object?
Zero objects that are not moving, have no momentum
How do we calculate momentum?
Momentum = mass(kg) x velocity(m/s)
What is the conservation of momentum?
In a closed system, the total momentum before event is equal to the total momentum after an event
Skater A bumps into another skater, Skater B. Skater B is stationary.
The skaters move off together in a straight line.
Explain what happens to the velocity of each of the skaters.
Use the idea of conservation of momentum.
-(total) momentum before
(collision) = (total) momentum
after (collision)
-momentum of skater A
decreases and momentum of
skater B increases
-velocity of skater a decreases and velocity if skater b increases
scalar quantity
-only has magnitude
vector quantity
-has magnitude and direction
Two bumper cars with equal momentum crash into each other and stop.
Explain why both bumper cars stop after the crash
-the momentum after the crash is 0
-because the momentum of the cars before the collision was equal and opposite
-so the total momentum before the collison was 0
-therefore momentum was conserved
