Unit 3: Dynamics Flashcards
Define mass:
Measure of the amount of matter in an object (measured in kg).
Property of mass:
Property of an object that resists change in motion. Greater mass = smaller change.
Define weight:
Effect of a gravitational field on mass (equal to product of its mass and acceleration of free fall, measured in N -> vector quantity).
Define free fall:
An object falling in free fall is falling solely under the influence of gravitational attraction.
In absence of air resistance, how does mass affect the acceleration of free fall?
No effect, they fall with the same acceleration.
How many Newton’s in a Meganewton?
1million Newtons - 1,000,000N
How many Newton’s in a Kilonewton?
1 thousand Newtons - 1,000N
What will happen when to an object when there is a resultant force? Which law?
Newton’s second law of motion tells us that objects will accelerate if there is a resultant force acting upon them (acceleration will be in the same direction as this resultant force).
Define resultant force:
Vector sum of all forces acting on a body.
Define acceleration:
The rate at which velocity changes with time.
Define linear momentum:
The product of mass and velocity (p = mv) (vector quantity).
Define force:
The rate of change of momentum.
Define Newton’s first law:
A body will remain at rest or move with constant velocity unless acted on by a resultant force.
What is it called when forces acting on an object are balanced?
The object is said to be in equilibrium (resultant force = 0).
Define Newton’s second law:
A resultant force acting on a body will cause a change in the object’s motion in the direction of the force AND the rate change of momentum is proportional to the magnitude of the force.
Define Newton’s third law:
Whenever two bodies interact, the forces they exert on each other are equal and opposite.
What conditions must be in place during Newton’s third law:
- The same type of force
- The same magnitude
- Opposite in direction
- Acting on different objects
What is a drag force?
Forces acting in the opposite direction to an object moving through a fluid.
Why does air resistance occur?
Air resistance occurs as the object moving through the air collides with the air particles. Air resistance is directly proportional speed.
What is air resistance?
Objects experience friction when moving through the air.
Factors of air resistance:
- Shape of the object
- Speed at which the object is travelling
What is terminal velocity?
When force of weight and force of air resistance are equal. Object stops accelerating and falls at constant speed/terminal velocity.
Define principle of conservation of momentum:
The total linear momentum before a collision is equal to the total linear momentum after a collision unless the system is acted on by a resultant external force.
What are external forces?
Forces that act on a structure from outside.
What are internal forces?
Forces exchanged by the particles in the system.
Define closed/isolated system:
System with no external forces.
Conservation of Momentum:
In a closed system with no external forces the momentum of the system before an event is equal to the momentum of the system after the event.
Momentum:
The product of an object’s mass and its velocity.
Newton’s First Law:
An object that is stationary or at constant velocity will remain stationary or at constant velocity unless acted on by a resultant force. (resultant force is zero)
Newton’s Second Law:
If an object is acted upon by a resultant force it will accelerate. The acceleration is inversely proportional to the mass of the object and directly proportional to the force acting on it.
Force:
The rate of change of momentum of an object. The product of the object’s mass with its acceleration.
Newton’s Third Law:
Every action has an equal and opposite reaction. If an object exerts a force on another object, then the other object must exert a force back, that is opposite in direction and equal in magnitude.
Terminal Velocity:
The maximum velocity an object can achieve. It is the point at which frictional forces and driving forces are balanced so no acceleration occurs and the resultant force on the object is 0N.
Upthrust:
The upwards force that a fluid applies on an object.
Weight:
The force of gravity on an object, the product of the object’s mass and the acceleration due to gravity.
