P10 - Force and Motion Flashcards
How the acceleration of an object depends on the size of the resultant force acting upon it
The greater an object’s resultant force, the greater the object’s acceleration.
Effect of an object’s mass on its acceleration
The greater an object’s mass, the smaller its acceleration for a given force.
How to calculate an object’s resultant force with acceleration and mass
resultant force (N) = mass (kg) x acceleration (m/s^2)
F = ma
Newton’s second law of motion
Object’s acceleration is directly proportional to the object’s resultant force ( F = ma )
Object’s acceleration is inversely proportional to object’s mass
What is meant by the inertia of an object?
Its tendency to stay at rest or in uniform motion
What is the inertial mass of an object?
A measure of the difficulty of changing an object’s velocity
Intertial mass can be defined as …
Force / acceleration
Difference between mass and weight
Object’s weight is the force acting on the object because of gravity,
Object’s mass is the quantity of matter in it.
An object acted on only by gravity accelerates at …
about 10 m/s^2
Terminal Velocity
The velocity an object eventually reaches when falling. The weight is then equal to the frictional force on the object.
The resultant force acting on an object that’s falling at terminal velocity
When an object’s moving at terminal velocity, the resultant force is zero.
Formula for weight
Weight (N) = mass (kg) x gravitational field strength (N/kg)
Gravitational field strength is essentially acceleration to a specific point.
[Terminal Velocity] The objects reaches constant velocity when …
The frictional force on it is equal and opposite to weight.
This velocity is called its terminal velocity.
The forces that oppose the driving force of a vehicle
Friction and air resistance.
What does the stopping distance of a vehicle depends on
On the thinking distance and the braking distance
Factors affecting stopping distance of a vehicle
High speed, poor weather conditions, poor vehicle maintenance affect braking distance
Poor reaction time AND high speed affect thinking distance.
High speed is the only factor that affects both braking and thinking distance.
How to estimate the braking force of a vehicle
Force (N) = mass (kg) x acceleration (m/s^2)
This gives the braking force of a vehicle
Thinking distance
The distance travelled by the vehicle in the time it takes the driver to react.
Braking distance
The distance travelled by the vehicle during the time the brakes are applied / the braking force acts.
How to calculate momentum
Momentum (kgm/s) = mass (kg) x velocity (m/s)
Momentum has both a size and a direction so it is a vector quantity.
The unit of momentum
kg m/s
What is a closed system? [aka Conservation of Momentum]
A system where the total momentum before an event is the same as the total after the event and no resultant force acts on any part of the system.
Two objects that push each other apart move ___ with ___ and ___ ___
Away with EQUAL and OPPOSITE MOMENTUM
What is meant when an object is called elastic?
If it returns to its original shape after removing the force deforming it.
How to measure the extension of an object when it is stretched
The difference between the length of the object and its original length.
How does a spring’s extension changes with the force applied to it?
Spring extension is directly proportional to the force applied, so long as the limit of proportionality is not exceeded. This relationship is linear.
What is meant by the limit of proportionality of a spring?
Beyond the limit, spring extension is no longer proportional to the applied force. This relationship becomes non-linear.
Hooke’s Law
Force applied (N) = spring constant (N/m) x extension (m)
Where else does Hooke’s law apply to an object?
When the object is compressed.
