Misc. Flashcards
Give three examples of a vector quantity
E.g. displacement, velocity, acceleration, force, momentum
What is meant by velocity?
The speed in a given direction
What is meant by the term “displacement”?
Distance an object moves, measured in a straight line from start to finish, with the direction of that line
When considering pairs of forces in Newton’s Third Law, what can you say about the forces?
They must be the same type of force, and on different objects
What are the changes to stored energy when a vehicle slows down?
The kinetic energy store of the object decreases, and the thermal energy store of the brakes increases
What is Newton’s Second Law of Motion?
The acceleration of an object is directly proportional to the resultant force acting on the object, and inversely proportional to the mass of the object (F=ma)
What is meant by the term “resultant force”?
The one single force that can replace a number of forces and has the same effect as all the original forces acting together
Define the specific heat capacity of a material
The amount of energy needed to raise the temperature of 1 kg of an object by 1 degree Celsius
What do physicists mean by the term “weight”?
The force due to gravity acting on an object
What is a free body force diagram?
A diagram showing all the forces acting on a single object only
Compare speed and velocity for an object moving at a constant speed in a circle
The speed is constant. The velocity changes, because the direction changes
State the equation for efficiency
Efficiency = useful energy output/total energy input
What equation links acceleration, change in velocity, and time?
Acceleration = Change in velocity/time taken
a = Δv/t
What is a scalar quantity?
A quantity with magnitude only
What is Newton’s Third Law of Motion?
When object A exerts a force on object B, object B exerts an equal and opposite force on object A
Give three examples of a scalar quantity
E.g. mass, distance, time, temperature, energy
Give an example of a non-useful energy transfer
E.g. transfer to the thermal store of the surroundings
What is the equation that links power, energy transferred and time?
Energy transferred = power x time
E = Pt
What is meant by dissipation of energy?
Energy becomes stored in non-useful ways (usually the thermal store of the surrounding)
Suggest ways in which efficiency of a machine could be increased
Use lubrication to reduce friction, use wires of a lower resistance
What is the acceleration of an object falling freely under gravity near the Earth’s surface?
9.8 m/s^2
How is weight calculated?
Weight = mass x gravitational field strength
W = mg
What can you say about the resultant force of an object moving at terminal velocity?
Resultant force is zero
What is meant by the “centre of mass” of an object?
The single point where the weight of an object may be considered to act
What is a vector quantity?
A quantity with magnitude and direction
Describe what happens to the half-life of a radioactive sample over time
Nothing, it stays constant forever
Name the magnetic pole at the arrowhead end of a compass
Magnetic north pole
Describe how a magnetic field diagram shows where the magnetic field is strongest
Where the magnetic field lines are closest together
Define half-life in terms of activity
The time it takes for the activity of a sample to halve
What does a north pole do to another north pole?
Repels
State the names for the two ends of a magnet
The north and south pole
Define half-life in terms of number of unstable nuclei
The time it takes for the number of unstable nuclei in sample to halve
Define induced magnet
A material which generates a magnetic field around it only when it is placed inside another magnetic field
Describe the relationship between the distance from a magnet and the strength of the magnetic field in that location
The greater the distance from the magnet, the weaker the magnetic field
Give two ways to find the shape of the magnetic field around a permanent magnet
Use a compass or sprinkle iron filings around the magnet
State what surrounds a permanent magnet
A magnetic field
State where the magnetic field is strongest around a permanent magnet
At the poles
State the direction in which magnetic field lines point
From north to south
State whether the force between an induced magnet and a permanent magnet is always attractive or repulsive
Always attractive
Name three magnetic chemical elements
Iron, nickel and cobalt
