Dynamics 2 Flashcards
What is Newton’s first law?
Every object will continue in its state of rest or uniform motion in a straight line unless a resultant force acts on it
When are Forces Balanced?
If resultant force is zero
What is Inertia?
The reluctance of the object to change it state of rest or motion, due to its mass
What is Newton’s second law?
When a resultant force acts on an object of constant mass, the object will accelerate in the direction of the resultant force
When are Forces Not balanced?
If resultant force is not zero
Equation for resultant force
F=ma
What is Newton’s third law?
If body A exerts a force on body B, body B will exert an equal and opposite force on body A
Condition for Newton’s third law
The 2 forces occur as an action-reaction pair
What is Friction?
Friction is a contact force that opposes or tends to oppose motion between surfaces in contact, due to irregularities on surfaces in contact
Positive Effects of Friction
Enhances grip
Ensures that objects can slow down when needed
How does Using Threads help to Enhance the Positive Effects of Friction?
To grip the road surface and roll without slipping
More grip to prevent skidding when it rains by channeling water out from under the tyres
How does Using a Parachute help to Enhance the Positive Effects of Friction?
To increase air resistance
To fall slowly and land safely by increasing surface area
How does Using Chalk help to Enhance the Positive Effects of Friction?
To absorb sweat and improve grip
Negative Effects of Friction
Wear and tear occurs
Efficiency of some objects is reduced
How does Using Wheels help to Reduce the Negative Effects of Friction?
Reduces friction due to circular shape
Smaller force can be applied to move objects around
How does Using Ball Bearings help to Reduce the Negative Effects of Friction?
Reduces friction between moving parts due to spherical shape
Prevents moving parts from rubbing against each other
How does Using Lubricants/Polished Surfaces help to Reduce the Negative Effects of Friction?
Adding a layer of lubricant between surfaces reduces friction
Polishing surfaces removes irregularities, reducing friction
How does Using an Air Cushion help to Reduce the Negative Effects of Friction?
Friction between 2 surfaces reduced when thin layer of cushion between surfaces exists
What happens when objects fall without Air Resistance?
Constant acceleration of 10m/s² downwards
Characteristics of Air Resistance
Always opposes motion of moving objects
Increases with speed of object
Increases with surface area/size of object
Increases with density of air
Objects falling with Air Resistance
Stage 1: After jumping, weight is a bigger force than air resistance, accelerates downwards
Stage 2: Air resistance increases until it is equal to weight, forces balanced and speed remains constant, known as terminal velocity
Stage 3: Parachute opened, air resistance increases dramatically, air resistance greater than weight, slows down
Stage 4: Air resistance reduces as object slows down until equal to weight, forces balanced and speed remains constant, new terminal velocity
