PHY136 - Introductory Physics I

1-D With the absence of air resistance, the idealized motion is called free-fall and the acceleration of a freely falling body is called the acceleration due to gravity near surface of the earth. All of the free fall objects withstand the same downward acceleration towards earth’s center. Relative Motion: Frame of Reference is a coordinate system plus a timer Velocity of Passenger Relative to Ground Velocity of Passenger relative to train Velocity of the relative to ground. 2-D T

Classes of forces: Contact / Field Forces, consist of Force and Mass Net force: the vector sum of all the forces acting on an object, written as . Directed by the free body diagram FREE BODY DIAGRAM: Drawing a systematic FBD, only consider the external force and not the internal force. Hooke’s law: a restoring force that exerts in the opposite direction of force applied K is the spring constant S is the change in the length caused by shift of the spring’s natural length

Centripetal on the FBD - force is directly to the center of the circle Mass is never a factor of any uniform circular motion Uniform Circular Motion Motion of an object traveling at a constant speed on a circular path Centripetal force is the that keeps an object in the circular path where T represent the period of the motion represents the centripetal acceleration represents the radius An object will travel tangential to its original circular motion once it loses the centripetal

Energy is conserved; can’t be created / destroyed Kinetic Energy describes motion => mv^2 Energy on earth originates from the sun Energy on earth is stored thermally and chemically Chemical energy is released by metabolism Energy is stored as potential energy in objects Conservation of Energy Energy cannot be created or destroyed, but can be transformed other energies of another form. Dissipation of “heat” – Energy could be lost by transforming into heat Work Work done is the dot product (scal

Momentum is defined by vector, p , such that it is the same as the product of mass and velocity p = mv This is the linear momentum, being a vector. Given the units being kg m/s By Newton’s 2nd law This general form includes the resulting from and vector sum of each individual momenta for any x particles in the system Any system that is not acted upon by an external force is an isolated system Given Internal Forces – within the system Given External Forces – from outside the system Pr

Parts of Rotational Motion Pure Translational Motion Pure Rotational Motion (around the axis of rotation) The general motion is the combination of these 2 parts Given that the rotational motion = 0 for linear motion Angular Motion Angular Displacement is the angle the object rotates through a rotational motion Δθ = θ2 – θ1 (SI unit is given as radian) 1 rad = 360° / 2π ≈ 57.3° x rad = arc length / radius => (θ rad = s/r) counter clockwise angular displacement is positive vice versa for the neg

The dynamics in the rotational motion is solely dependent on Newton’s 2nd law. The effect is the application of torque. Torque , for r is the distance from the center of rotation. for that l is the lever arm directly perpendicular Torque is the cross product of the force applied and the radius times sin θ It is a vector CCW τ is positive and CW τ is negative Internal forces do not contribute to Στ Center of Gravity W = weight With a symmetrical shape, the center of gravity is at the geom

Stress Stress is formally defined as force per unit area known as Pascal (Pa) Tensile stress - opposed force stretch the bone Forces that cause stretching in the material creating tension Shear stress - opposed forces twist the bone Compressive stress - opposed forces compress the bone Compression of the object which causes spring‐like behaviour Volume stress - water pressure squeezes the swimmer Strain Strain is the reaction to stress (unitless) It is due to change in shape (shear stress)

The Nature of Waves Types Mechanical (water, sound, seismic) Requires a real/mechanical medium Electromagnetic (light, radio, television, micro, x-­rays, radar) Comes from oscillations of electric field Matter (electrons, protons, atoms, molecules) Water wave’s commonality to all waves: A wave is a traveling disturbance A wave carries energy from place to place Transverse Waves The wave is one in which the disturbance is perpendicular to the direction of travel of the wave Longitudinal Waves T