Mechanics Flashcards
What does ‘mechanics’ in physics study?
Mechanics deals with the behavior of physical bodies under forces or displacements, including statics, kinematics, and dynamics.
State Newton’s First Law of Motion.
A body remains at rest or moves with constant velocity in a straight line unless acted upon by an external force.
State Newton’s Second Law of Motion.
The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass: F = m a.
State Newton’s Third Law of Motion.
For every action force, there is an equal and opposite reaction force.
What is the definition of kinematics?
Kinematics is the branch of mechanics that describes motion without considering forces that cause it.
Differentiate between distance and displacement.
Distance is the total path length traveled; displacement is the straight-line change in position with direction.
What is velocity?
Velocity is the rate of change of displacement with respect to time, including direction (v = Δs / Δt).
What is acceleration?
Acceleration is the rate of change of velocity with respect to time (a = Δv / Δt).
Give the equation for constant acceleration motion (SUVAT equation).
s = ut + ½at² (where s = displacement, u = initial velocity, a = constant acceleration, t = time).
What is uniform circular motion?
Motion in a circle at constant speed, where velocity’s direction changes constantly, requiring a centripetal force.
Define centripetal force.
The net inward force on an object moving in a circular path, given by F = mv² / r.
What is inertia?
Inertia is the tendency of an object to resist changes to its state of motion (related to mass).
How is momentum defined?
Momentum (p) is the product of an object’s mass and its velocity: p = m v.
What is impulse and its relation to momentum?
Impulse is the change in momentum, calculated as Force × Time = Δp.
State the principle of conservation of momentum.
In a closed system, the total momentum before an interaction equals the total momentum after the interaction.
Define work in the context of mechanics.
Work (W) is done when a force causes displacement: W = F × d × cos(θ).
How is energy defined?
Energy is the capacity to do work; it exists in various forms (kinetic, potential, thermal, etc.).
Give the formula for kinetic energy.
Kinetic Energy (KE) = ½ m v².
Give the formula for gravitational potential energy.
GPE = m g h, where g is gravitational acceleration and h is height above a reference.
What is the definition of power in mechanics?
Power (P) is the rate of doing work: P = W / t or P = F v (for constant force and velocity).
Explain what friction is.
Friction is a force opposing relative motion between two surfaces in contact.
Differentiate between static friction and kinetic (sliding) friction.
Static friction acts when there is no relative motion; kinetic friction acts when surfaces are sliding past each other.
What is the coefficient of friction?
A dimensionless number (μ) representing friction level between two surfaces; F_friction = μ × Normal Force.
Define torque (moment of a force).
Torque = Force × Perpendicular distance from pivot, causing rotational motion.
What is equilibrium in mechanics?
A state where the net force and net torque on a body are zero, so there’s no linear or rotational acceleration.
What does ‘center of gravity’ mean?
The point at which an object’s entire weight can be considered to act for balancing and stability purposes.
Explain the principle of moments.
For rotational equilibrium: Sum of clockwise moments = Sum of counterclockwise moments about a pivot.
What is a simple machine?
A basic mechanical device (lever, pulley, inclined plane, screw, wheel & axle) that changes force magnitude or direction.
Define mechanical advantage (MA).
MA = Load / Effort, or Output Force / Input Force, for a simple machine.
Why is mechanical efficiency usually less than 100%?
Friction and other energy losses convert some input energy into heat or other non-useful forms.
What is the difference between statics and dynamics?
Statics deals with forces in systems at rest (no acceleration), while dynamics studies forces and motion in accelerating systems.
