P2 Flashcards
What units can distance be measured in?
mm, cm, m, and km.
What units can time be measured in
ms, s, mins, and hours.
What is the formula for speed?
Speed = Distance / Time
Q: What is a scalar quantity?
A quantity that has magnitude only.
What is a vector quantity?
A quantity that has both magnitude and direction.
Can scalar quantities be negative?
no, but vector quantities can be, as sign indicates direction.
Is speed a scalar or vector?
Scalar
Is velocity a scalar or vector?
Vector
Is displacement a scalar or vector?
Vector
Is distance a scalar or vector?
Scalar
What does the gradient of a distance-time graph represent?
Velocity (speed).
What does a steeper gradient on a distance-time graph mean?
faster speed.
What does a negative gradient mean?
The object is returning to the starting point
What does a horizontal line mean?
The object is stationary.
What does a curved line on a distance-time graph represent?
Changing velocity (acceleration or deceleration).
What does the gradient of a velocity-time graph show?
Acceleration
What does a steeper gradient mean on a velocity-time graph?
Greater acceleration.
What does a negative gradient represent?
Deceleration.
What does a horizontal line mean?
Constant velocity.
What does the area under a velocity-time graph show?
Total displacement - whereas speed/time graph is total distance
If velocity is always positive, then displacement will be same as distance
What does a curved line indicate on a velocity-time graph?
Changing acceleration.
How is average speed calculated?
Average speed = Total distance / Total time
What is an electrostatic interaction?
A force of attraction or repulsion between charged particles.
What is gravitational attraction?
A force between objects with mass.
What are contact forces?
Forces that act when objects are in contact, such as friction.
What is friction?
A contact force that opposes motion between surfaces or in a fluid.
What causes a magnetic attraction.
A material that has the ability to physically attract other magnetic substances
What does a free body diagram show?
The direction of forces acting on an object.
In which direction does the reaction force act?
Normal (perpendicular) to the line of contact - eg. the surface a car drives up a hill on
In which direction does friction act?
Opposite to movement, along the line of contact - eg. downwards if a car is going up a hill
In which direction does weight act?
Vertically downward from the object’s centre of mass
What does the length of a force arrow represent?
The size (magnitude) of the force.
What does a longer arrow in a diagram show?
A greater force and the resultant force.
What happens if arrows are equal and opposite?
Forces cancel out and the object is in equilibrium (constant velocity).
What does Newton’s First Law state?
An object stays at constant velocity unless acted on by a resultant force.
What happens when a resultant force acts on an object?
It accelerates (change in speed or direction).
What happens initially when a car starts moving?
Low air resistance (drag) so thrust is opposed mostly by friction.
What happens as the car speeds up?
Air resistance increases, reducing net acceleration.
When does the car reach terminal velocity?
When thrust is balanced by drag and friction—no resultant force, no acceleration.
What is Newton’s Second Law formula?
F = m × a (Force = mass × acceleration)
What is inertia?
A measure of how difficult it is to change an object’s velocity (depends on mass).
How do you calculate inertial mass using force and acceleration?
m = F / a
What is the formula for momentum?
p = m × v (momentum = mass × velocity)
What are the units of momentum?
kg·m/s or Ns
What is conserved in an elastic collision?
Both momentum and kinetic energy.
What is the total momentum before firing a bullet from a stationary gun?
0 (both are stationary).
What is the momentum after firing?
Bullet momentum = Gun momentum (in opposite directions).
How do you calculate the recoil speed?
Recoil velocity of gun = (mass of bullet x velocity of bullet) / mass of gun
What does Newton’s Third Law state?
Every action has an equal and opposite reaction.
Example of Newton’s Third Law with a book?
Book’s weight is balanced by the support force from the table.
Example with a rocket?
Force of ejected gases = Force lifting the rocket.
What is the formula for work done?
Work = Force × Distance (W = F × d)
What are the units for work done?
Joules (J)
Example of work done?
Lifting a book 1m transfers energy from muscles to gravitational potential.
Power equation
Power (w) = work done (J) /time (s)
What is power?
Amount of energy that is transferred per second - rate at which energy is transferred when doing work
What happens when a single force is applied to an object?
It moves in the direction of the force.
What must happen for an object to stretch, bend, or compress?
More than one force must be applied.
What is deformation?
A change in shape caused by a force (also called distortion).
What is elastic deformation?
The object returns to its original shape when the load is removed.
What is plastic deformation?
The object does not return to its original shape after the load is removed.
What is the formula for Hooke’s Law?
F = k × x (Force = spring constant × extension)
What does each symbol represent in Hooke’s Law?
F = force (N), k = spring constant (N/m), x = extension (m)
What does a linear Force-Extension graph show?
Elastic behaviour — follows Hooke’s Law.
What is the elastic limit?
The point beyond which the material no longer behaves elastically. - from this point it will not follow hook’s law
What does a non-linear graph represent?
Plastic deformation — does not obey Hooke’s Law.
What does a shallow gradient on the graph indicate?
A small force produces large extension — plastic deformation.
What happens if the graph is only linear?
The material is brittle — snaps after the elastic limit.
What does the area under a force-extension graph represent?
Work done on the spring.
How do you calculate work done on a spring?
Work = ½ × k × x²
What does all matter with mass have?
A gravitational field.
What is weight?
The force on a mass due to gravity.
What is the formula for weight?
Weight = mass × gravitational field strength (W = m × g)
What unit is weight measured in?
Newtons (N)
How is weight measured?
With a Newton meter (force meter).
Does mass change on different planets?
No — mass stays the same, but weight changes with gravity.
What is the formula for gravitational potential energy?
GPE = mass × gravitational field strength × height (GPE = m × g × h)
What are the units of GPE?
Joules (J)
What is the value of g (on Earth)?
10 m/s²
What happens when a force is applied to an object about a pivot?
It causes rotation due to a moment.
What is the formula for moment?
Moment = Force × Perpendicular Distance (M = F × d)
What is a common real-life example of a moment?
Pressing a bike pedal causes rotation.
When is an object in rotational equilibrium?
When clockwise moments = anticlockwise moments.
What can gears change?
Speed, force, or direction by rotation
What happens when a small gear drives a large gear?
The large gear turns slower but with more force.
Why does a gear with fewer teeth spin faster?
Less opposing force and faster rotation.
What is the key phrase used to describe a lever?
A force multiplier - transmits force by rotating about a pivot
What is the force you exert on the lever?
The effort
What is the force that the lever exerts on the object?
The load
Ratio of load to effort is called?
Mechanical advantage
How to calculate moment from effort or load?
Moment = effort/ load x distance from, pivot to effort/load
What is the formula for pressure?
Pressure = Force / Area (p = F / A)
What direction is the force from fluid pressure?
At right angles (normal) to any surface.
Why is lying on a bed of nails less painful than on one nail?
The force is spread over a larger area, reducing pressure.
What principle do hydraulic brakes work on?
Pressure is constant in a fluid.
Why do wider cylinders produce more braking force?
Greater area leads to a greater force to maintain constant pressure.
What happens when a piston is pushed in a narrow cylinder?
The force is transmitted to a wider cylinder, multiplying the braking force.
