🗊Презентация Mechacnics. Molecular physics and Thermodynamics. Electricity. Magnetism

Republic of Kazakhstan Republic of Kazakhstan Ministry of Education and Science Kazakh-British Technical University Faculty of Power and Oil and Gas Industry Physical Engineering Department Physics 1 Voronkov Vladimir Vasilyevich

Physics 1 Mechacnics Molecular physics and Thermodynamics Electricity Magnetism

Lecture 1 SUBJECTS: Mechanics Kinematics Rectilinear motion Projectile motion Uniform circular motion

Mechanics Mechanics is the science of motion and its cause. Kinematics is the mathematical description of motion.

Main terms of Kinematics Displacement is the change in the position of an object. one-dimensional: ∆x= x2 - x1 many-dimensional: Average velocity is the distance traveled per unit of time: Instantaneous velocity is the velocity at infinitely small interval: or the same

Average acceleration is the total change in velocity per unit of time: Average acceleration is the total change in velocity per unit of time: Instantaneous acceleration is the change in velocity per unit of time at infinitely small time: Gravitational motion is the motion when gravitational acceleration g=9.8 m/s2 takes part. For example: rocket motion.

Displacement at constant acceleration in rectilinear motion : Displacement at constant acceleration in rectilinear motion : Where r0 and V0 is initial displacement and velocity at t=0, a is constant acceleration.

Rectilinear motion in graphics A) Object stands still. B) Object moves with constant speed.

Another example of rectilinear motion

The car motion in table The car motion in table

Velocity and acceleration

Projectile motion is a gravitational motion but the object has no its own acceleration. So the motion goes with constant gravitational acceleration. For example: cannonball motion. Projectile motion is a gravitational motion but the object has no its own acceleration. So the motion goes with constant gravitational acceleration. For example: cannonball motion. Usual method for solving projectile motion problems: Separate the motion into two parts: vertical and horizontal: so we have: two coordinates x and y two velocities Vx and Vy one acceleration ay =-g, and ax=0

Then one should determine the elevation angle Θ0 - the initial angle to horizon. Then one should determine the elevation angle Θ0 - the initial angle to horizon. So the trajectory of an object in the gravitational field can be described as following: x= V0CosΘ0 t, y= V0SinΘ0 t – gt2/2. Let’s designate R as the range the object travels from zero height (y=0) till its fall (y=0 again) then we can calculate it as R=V02Sin(2Θ0)/g. Flight time t: it’s easy (using the equation dy/dt = 0) to find that the time of ascent is V0SinΘ0/g, then the full flight time is double: tflight= 2V0SinΘ0/g. Using the flight time one can find: the maximal height, the range of flight (the maximum range of flight from zero height (y=0) till the fall of the object (y=0 again)).

Circular uniform motion Uniform circular motion is performed with constant speed along a circular path. Circular motion is a special case of motion on a plane. Its coordinates is angular coordinate φ and radius r. The angular speed is defined as: The linear speed relates to the angular speed as: Period T is the time of one full revolution: T= 

Units in SI Displacement x,y m Velocity V m/s Acceleration a,g m/s2 Angle φ rad Angular speed  rad/s Period T s

Read before the next Lecture Fishbane Chapters 4,5 pp.87-150 Russian equivalents: Трофимова Т.И. Курс физики. Глава 2 Динамика материальной точки. Савельев И.В. Курс общей физики. Т.1. Глава 2 Динамика материальной точки.