NUB Physics (PH 101) Lecture 2 PDF

Lecture-2 Physics (PH 101) Prepared by Prof. Wael Zakaria Tawfik Tel : 01127657166 E-mail : [email protected] Motion 2  Motion Everything in the universe moves. It might only be a small amount of movement and very very slo...

Lecture-2 Physics (PH 101) Prepared by Prof. Wael Zakaria Tawfik Tel : 01127657166 E-mail : [email protected] Motion 2  Motion Everything in the universe moves. It might only be a small amount of movement and very very slow, but movement does happen. Don't forget that even if you appear to be standing still, the Earth is moving around the Sun, and the Sun is moving around our galaxy. The movement never stops. 3  Laws of Motion Newton’s laws of motion in a brief description: First Law: Any object will continue to remain in its existing state of motion or rest unless a net external force acts on it. Second Law: If an object has a certain mass, greater the mass of this object, greater will the force required be to accelerate the object. It is represented by the equation F = ma, where ‘F’ is the force on the object, ‘m’ is the mass of the object and ‘a’ is the acceleration of the object. Third Law: For every action, there is an equal and opposite 4 reaction.  Types of Motion in Physics 1-Translational Motion – It is the type, where an object moves along a path in any of the three dimensions like the motion of a train. 2-Random motion- It is The disordered or irregular motion of a body like the random motion of gas molecules and the motion of insects and birds. 3-Periodic Motion – It is the type of motion that repeats itself after certain intervals of time. 4-Wave Motion Wave motion is the transfer of energy and momentum from one point of the medium to another point of the medium without actual transport of matter between two points. 5 5-Circular motion The motion of an object in a circular path is known as circular motion. Examples of circular motion in daily life -The motion of the electron around the nucleus -The motion of toy car on the circular track -The motion of planets around the sun 6-Vibrational motion It is the motion of a body about its mean position like the motion of the pendulum of a clock about its mean position. 7-Harmonic motion 6 Any motion that can be described by using Sin or Cos.  Circular Motion To describe the translational motion, we will talk about: -Position -Velocity -Acceleration Let us now consider the special case in which the path is a circle; i.e., circular motion. Angular Linear Motion Motion Displacement L θ Velocity w Acceleration a 7 (w) (a) 8  Circular Motion The following figure represents an object that is moving in a circular path from A to B with radius r=OB. 9 The angular velocity may be expressed as a vector quantity 10 11 For the angular acceleration (α): By integrating both sides: By integrating both sides, we find 12 We have explained position, angular velocity and angular acceleration so, angular motion has been described. 13 NewtoN’s Laws 14 Exercises 15 16 17 Q4 : A disk speeds up from rest at a constant rate of 2.5 rad/sec2. a)What is the final angular speed of the disk after 18 sec? b)What is the linear speed of a point at the edge of the disk after 18 sec. (The radius of the disk is 50 cm) Sol. α=2.5 rad/s2 , t=18 sec , r=50 cm =0.5 m ωf = ωi +αt = 0+2.5×18 = 45 rad/sec υ=ωr=45×0.5 =22.5 m/s 18 THANKS 19