P2.2: Newton’s Laws - Incomplete Flashcards
What does Newtons first law state?
An object will remain stationary or at a constant velocity unless acted upon by an external force
What does Newtons 2nd law state?
The force acting on an object is equal to its rate of change of momentum
What formula is used to calculate the resultant force?
F = ma
What is resultant force?
the overall force that acts on the object
What happens if an object has zero resultant force?
It would remain stationary
OR
Maintain a constant velocity
What does friction do?
Makes things slow down and stop
How can you prevent friction from stopping you from moving?
Need a driving force to keep moving
What happens when the driving force is equal to the friction force
Move at a steady speed
What happens when the driving force is greater than the friction force
Object will accelerate
What happens when the driving force is less than the friction force
Object will decelerate
Where does friction occur?
Between 2 surfaces in contact
When does drag occur?
When an object passes through a fluid
Boat and water
What is an example of a type of drag?
Air resistance
What happens to the resistance when te velocity of an object increases?
Resistance also increases
How does an object reach terminal velocity?
When objects first set off, more driving force than friction: acceleration
As velocity and resistance increase, acceleration is reduced and until friction force is equal to driving force
Forces balanced - terminal velocity
What is terminal velocity?
When friction forces are equal to the driving force and there are no resultant forces
What is inertia?
The measure of how difficult it is to change an objects velocity
What is inertia dependant on?
Mass - larger mass means larger intertia
What does Newtons 3rd law state?
When two objects interact, the forces they exert on each other are equal and opposite
How are mass momentum and velocity connected?
The greater the mass of an object and the greater the velocity, the more momentum an object has
What equation links mass momentum and velocity?
Momentum (kg m/s) = mass (kg) x velocity (m/s)
Is momentum a vector or scalar?
Vector - has size and direction
What is momentum?
A measure of how hard it is to stop a moving object
When pushing against a wall, the wall pushes back with an equal and opposite force.
This force is called:
The normal contact force
The formula for momentum is:
p=mv
How can acceleration change an objects momentum?
Velocity will increase which means the momentum is also increased
If a hand pushed an object and changed its momentum, how could we calculate the force that the hand used to push the object?
If you calculate the change in momentum and divide it by the time in seconds. Answer given in newtons
Why is it important that a car is built with seat belts, crumple zones and airbags in the scenario of a car crash?
If a car smashes into a wall for example, the momentum will almost instantly decrease to zero. This will cause a huge force exerted in the opposite direction towards anyone inside the car. This could cause the people to experience spinal injuries or head trauma. To reduce the chance of this, the change in momentum should be spread over a longer period of time to reduce the force. This gives a small amount of extra time for the car to lose momentum slower.
Energy is never created or destroyed, it is only ever…
Transferred between different forms and objects
What are examples of different transferred energy stores?
Thermal
Gravitational potential
Magnetic
Elastic
Kinetic
Nuclear
Electrostatic
Chemical
What is a system?
Particular object or groups of objects, the collection of the matter is known as a system
When a force makes an object move…
Energy is transferred and work is done
What is power?
The rate at which energy is transferred
What is the formula for power?
Work done / time
What is the formula for work done?
Force x distance
What are the different ways energy can be transferred?
Mechanically
Electrically
Through heating
Via infrared radiation
Via light and sound waves
What can an open system do?
Lorse or gain energy from the ‘outside world’
What is one joule equivalent to?
One newton-metre
