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1. DYNAMICS OBJECTIVES: In this chapter we will learn : Some important kinds of Forces such as ; NORMAL & FRICTION Forces The Laws of Motion How to solve dynamics problems by the Laws of Motion

2. DYNAMICS 1. NORMAL Force: is the relation between FORCE & MOTION is REACTION Force, perpendicular to the surface that the action force is applied FORCE: is the Effect that can destroy, stop or move the objects. Since it shows a DIRECTION. Then it is a VECTOR Quantity. THE KINDS OF FORCES

3. FRICTIONAL FORCE Frictional force: It is an important force which only acts when two objects are touching and are applying force to one another. It is a force that slows down moving objects and brings them to rest. It always acts in a direction opposite to the direction of the force applied to the object. Walking is possible only on a frictional surface. Water also applies a frictional force to the objects moving in it. Frictional force does not depend on the area of the rubbing surfaces. The frictional force between the object and the table depends on two factors; a. The weight of the object. b. The roughness of the surfaces rubbing together.

4. 2. FRICTION Force: Ex: Find the friction force in both case. is REACTION Force, formed in opposite direction to the action force applied. Between two surface, there is a maximum value of Friction Force. Let us write an equation about this maximum friction force between two surface. We call this constant as the coefficient of friction, µ between two surface

5. Planet Field Strength Mass Weight 151 N 358 N 400 N 67 N 152 N 1067N 428 N 368 N 480 N 12 N X X X X X X X X X X 3,78 N/kg 8,94 N/kg 10 N/kg 1,7 N/kg 3,79 N/kg 25,4 N/kg 10,7 N/kg 9,2 N/kg 12 N/kg 0,3 N/kg 40 kg 40 kg 40 kg 40 kg 40 kg 40 kg 40 kg 40 kg 40 kg 40 kg = = = = = = = = = = Mercury Venus Earth Moon Mars Jupiter Saturn Uranus Neptune Pluto 3. TENSION Force: is ACTION-REACTION Force, formed along stretch Force applied. Ex: What is the weight of an object on the Moon which has the weight on Earth as 100N ? 4. GRAVITATIONAL Force: is Natural Attractive Field Force, between two bodies that appears as the WEIGHT. 5. MAGNETIC Force: 6. ELECTROSTATIC Force: 7. NUCLEAR Force: We define the Gravitational Field as;

6. LAWS OF MOTION II-) ACTION PRINCIPLE: If the NET FORCE is not ZERO on an object ; I-) INERTIA PRINCIPLE: Either the object will be accelerated or decelerated INERTIA: is the tendency to keep the initial position PRINCIPLE: If the NET FORCE is ZERO on an object ; Either the object stops or moves steadily (with constant velocity) III-) ACTION-REACTION PRINCIPLE: If an object applies a Force on another object. The Other One replies with the same Force in opposite direction

7. INCLINED PLANE: Along x-axis, There is motion. If there is no FRICTION, then take; Object is sliding down. Along y-axis, There is no motion.

8. LIFT PROBLEMS: B- The Lift accelerated downward or decelerated upward ; Let us look at the cases by both the observers inside the Lift and outside the Lift A- The Lift accelerated upward or decelerated downward ;

9. Apparent Weight W = m(g+a) W = m(g-a) Weightless W = mg

10. Ex.:A force of 10N is applied on the mass of the 2kg with and angle of 370. If the coefficient of friction between mass and surface is 0.1, what is the acceleration of the mass in m/s2 ? Ex.:What is the acceleration of the object, a=? m=10 kg m=2 kg Along y-axis; There is no MOTION, ay=0 Along x-axis; There is MOTION, a=ax Along y-axis; There is no MOTION, ay=0 Along x-axis; There is MOTION, a=ax

11. Ex.: Two masses which are contact with each other are pushed by a force of 20 N. What force does the mass A apply to the mass B when coefficient of friction between the masses and the surface; µ=0 and µ=0.1? Ex.: Three masses are connected with ropes. A force of 280 N acted on the masses as shown in the figure. Find the tensions in the rope T1 ,T2 . m1=3kg m2=2kg Along y-axis; There is no MOTION, ay=0 Along x-axis; There is MOTION, a=ax For Reaction Force, R; Choose one of the masses, ex; m2 For Reaction Force, R; Choose one of the masses, ex; m2

12. Ex.: Two masses are connected to each other as shown in figure are pulled up by force F. If the tension in the cord is 42N what is the force F? Ex. ( Atwood Machine) : When the system is released , find the tension in the rope in N, T= ?

13. Ex.: Find acceleration of the system and T1 & T2 When the coefficient of friction between 10kg of mass and the surface,µ=0 and µ=0.1? Ex.: When the system is released, what is the Acceleration of the system. The coefficient of friction is µ=0,1.

14. Ex.: In the figure the coefficient of kinetic friction is µ for all interacting surfaces. Find the accelerations of the blocks a. Ex.: Find the velocities of the objects K and L shown in figure .3 seconds later, after they are released.

15. Ex.: The objects K and L are released in a frictionless system as shown in figure. Find the tension T on the rope which joins the objects K and L . mK=mL=1kg

16. CHECKING OF UNDERSTANDING (HOMEWORK) The Answers of them should be placed just after this Chapter before the Next Chapter. 1. What is Force? How many kinds of Forces are there? 2. Why do we need to use the kind of ``NORMAL FORCE``? 3. What are the factors that the force of friction depends on? 2. What is the difference between uniform motion and uniformly accelerated motion? 3. Driving on an icy high way is particularly dangerous. Why? 4. What is INERTIA and its Principle? Give some examples 5. You hit a ball with your foot. Since the forces are F and –F can you say the total force is zero? Then why does the ball start to move? 6. The x-component of the projected objects is always constant , why? 7. Mostly which Law of Motion is used to solve Dynamics Problems? 8. What is Atwood Machine? And how do we find the acceleration of it? 9. Can we feel ``Weightlessness`` on Earth? How?