dynamics part 2 Flashcards
(16 cards)
what are the effects of a force on the motion of a body?
- a body at rest moves
- a moving body increases im speed
- a moving body decreases in speed
- a moving body changes direction
from the above, a force can cause an object to accelerate (or decelerate) as a result of change in velocity
however, even when acceleration is zero, the object can be stationary or moving with constant velocity, and there still are forces acting on an object but the resultant of the these forces is zero.
what is newton’s first law?
N1L states that every object will continue in ints state of rest or uniform motion in a straight lime unless a resultant force acts on it
what is inertia?
the inertia of an object refers to the reluctance of the object to change its state of rest or motion due to its mass
what is mass?
mass is the property that resists the change in motion
an object with grater mass will have greater inertia (and the harder it will for it to start moving, slow down, move faster or change direction)
what is newton’s second law?
N2L states that when a resultant force acts on an object of a constant mass, the object will accelerate in the direction of the resultant force.
what is formula of N2L
F = ma
what does N2L formula show?
Newton’s Second Law of Motion tells us that:
• a resultant force F on an object produces an acceleration a
• doubling the resultant force F on an object doubles its acceleration a
• with the same resultant force F, doubling the mass m halves the acceleration a
what is newton’s third law?
Newton’s Third Law of Motion states that if body A exerts a force FAB on body B, then body B will exert an equal and opposite force FA on body A.
Each action-reaction pair are equal in magnitude but act in opposite directions.
what does N3L show?
Newton’s Third Law of Motion tells us four characteristics of forces:
1. Forces always occur in pairs. Each pair is made up of an action and a reaction forces.
2. Action and reaction forces are equal in magnitude.
3. Action and reaction forces act in opposite directions.
4. Action and reaction forces act on different bodies.
what are free body diagrams?
diagrams where arrows are used to represent forces acting on individual objects
what are vector diagrams
diagram which is used to add up vectors by graphical method where arrows are drawn to represent the vector quantity and find the resultant force
take note: forces acting on an object form a closed triangle if they are in equilibrium
what is friction? and what is its effect on motion?
friction is the contact force that opposes or tends to oppose motion between surfaces in contact
frictions acts in opposite direction of the force applied and causes the object to slow down and come down to a stop eventually
what are the advantages and disadvantages of friction? how do we enhance/reduce them?
advantages:
• Allows us to walk without slipping
• Enables vehicles to move and stop
• Helps in holding and gripping objects
enhancing them:
using treads/ using parachute/ using chalk
disadvantages:
• Causes wear and tear of moving parts
• Reduces efficiency by producing unwanted heat
• Wastes energy in machines
• Makes movement harder (requires more force)
reducing them:
using wheels / using ball bearings / using lubricants
what is free fall? (objects falling wo air resistance)
an object in free fall happens only when its own weight is the only force acting on it
acceleration of free-falling objects=
at a constant acceleration of 10m/s2
direction of motion is downwards (towards the centre of earth)
does not depend on their mass or size
what happens when objects fall with air resistance?
air resistance:
- opposes the motion of moving objects
- increases with the speed of objects
- increases with the surface area of the objects
- increases with the density of air
how it affects:
surface area = larger surface area increases air resistance (more air particles hit the object) - slows down more/falls at lower acceleration
speed = speed increases, air resistance increases (the object collides with more air particles per second) - slow down more
weight = greater mass, heavier the object, more air resistance required to balance the larger weight, so falls at a higher speed to reach terminal velocity ( thus heavier objects have higher terminal velocity )
what is terminal velocity?
when the air resistance acting against an object equals its weight, causing it to fall at constant speed
(0 acceleration)
