Download Mechanics: Distance, Displacement, Speed, Velocity, Acceleration, and Projectile Motion and more Study notes Physics in PDF only on Docsity! TOPIC 2 MECHANICS DISTANCE AND DISPLACEMENT DISTANCE: a scalar quantity which measures how far two locations are apart from each other along a certain path - all twists and turns of the path included - how far something has traveled w/out regard to the direction DISPLACEMENT: a vector quantity defined by the length and direction of the line segment joining the initial and final positions of an object - "change in position" - distance traveled + direction SPEED AND VELOCITY SPEED: scalar ⇒ distance moved in a given amount of time VELOCITY: vector ⇒measure of how fast an object moves through a displacement ACCELERATION - vector - rate of change of velocity ACCELERATION DUE TO GRAVITY OF ANY FREE FALLING OBJECT is given by g = 9.81m/s² ⇒ does not depend on the mass of the object FREEFALL: ignore the effect of air resistance on an object falling down to earth due to gravity ⇒ uniformly accelerated motion as the only force acting on the object is that of gravity *acceleration is a vector so has a direction -> assume the upwards direction to be positive, the acceleration due to gravity would have a negative value of g = -9.81m/s² INSTANTANEOUS: the instantaneous value of speed, velocity, or acceleration is one that is at a particular point in time AVERAGE: average value of speed, velocity or acceleration is one that is taken over a period of time RELATIVE VELOCITY: the velocity of an object B in the rest frame of another object A EXAMPLE: a motorcycle travelling on the highway at a velocity of 120 km/h passes a car travelling at a velocity of 90 km/h SUVAT EQUATIONS the equations of uniformly accelerated motion can only be under conditions where the acceleration is constant GRAPHS DESCRIBING MOTION DISPLACEMENT-TIME GRAPH - gradient is velocity - the negative gradient is returning back to the starting point - a horizontal line means it is stationary - a curved line means that the velocity is changing and its accelerating VELOCITY-TIME GRAPH - gradient is acceleration - the negative gradient is deceleration - a horizontal line means constant speed - the area under the line is the distance traveled - a curved line means that the acceleration is changing DETERMINING THE RESULTANT FORCE 1. resolve all acting force into horizontal and vertical components 2. add up the horizontal components 3. add up the vertical components 4. combine the sum of horizontal components and the sum of horizontal components and the sum of vertical components TRANSLATIONAL EQUILIBRIUM A body is said to be in translational equilibrium if the net force acting on the body is zero ● the body is either at rest or travels at constant velocity EG: mass hanging at rest, elevator moving upwards at constant velocity, parachutist reaching terminal velocity WORK, ENERGY AND POWER KINETIC ENERGY: the energy of a body due to its motion GPE: changes with its height ELASTIC POTENTIAL ENERGY: stored as a result of the deformation of an elastic object such as the stretching of a spring WORK DONE: the transfer of energy due to a force ⇒ scalar quantity ● In a force displacement graph: Work Done is the AREA UNDER THE CURVE POWER: work done or the energy output per time given * for constant force acting on an object with constant velocity, the power is given by the equation: P = Fv PRINCIPLE OF CONSERVATION OF ENERGY Energy can neither be created or destroyed, it can only be changed from one form to another EG: an electrical heater transforms electrical energy to thermal energy, a falling object transforms GPE to KPE Total energy of an isolated body remains constant⇒ ΔKE + ΔGPE = 0 EFFICIENCY: ratio of useful output to energy input as the % MOMENTUM AND IMPULSE NEWTON’S SECOND LAW EXPRESSED IN TERMS OF RATE OF CHANGE OF MOMENTUM Linear momentum (p) is a vector ⇒ same direction as the velocity of the object UNIT: kg﹒ms⁻¹ The change of momentum (Δp) is called IMPULSE IMPULSE AND FORCE-TIME GRAPHS: impulse is the area under the force-time graph CONSERVATION OF LINEAR MOMENTUM THE LAW OF CONSERVATION OF LINEAR MOMENTUM: the sum of initial momentum is equal to the sum of final momentum in a closed system COLLISIONS TYPE TOTAL MOMENTUM TOTAL KE ELASTIC conserved conserved INELASTIC conserved not conserved EXPLOSION conserved not conserved
