Ch 4 Phy Class 9
Important Easy Notes of Ch 4 Phy Class 9 English Medium written by Professor Mr. Samiullah Suib. These notes are very helpful in the preparation of Physics for students of the 9th class Physics English Medium and these are according to the paper patterns of all KPK Book Boards.
Summary and Contents:
Topics which are discussed in the notes are given below:
- Definition of force and diagram with examples
- Definition of parallel forces with examples.
- Types of parallel forces: (i) like parallel forces (ii) unlike parallel forces.
- Definition of like parallel forces with examples.
- Definition of unlike parallel forces with examples.
- Definition of addition of forces: mathematical form.
- Addition of like parallel forces with examples and Addition of un-like parallel forces with examples.
- Definition of Non parallel forces with examples.
- State and explain had to tell role with examples.
- Definition of resolution of forces and also explanation.
- Definition of a rectangular components and also explain.
- Components are represented in terms of force.
- Magnitude of resultant force and direction of resultant force.
- Definition of rotational motion with examples.
- Definition of rigid body with examples.
- Definition of centre of mass with examples.
- Definition of centre of gravity with examples.
- Centre of mass of some objects
- Differentiate between centre of mass and centre of gravity.
- Derivation and meaning of torque
- Definition of torque: other name of torque, symbol, mathematical form, unit, quantity, nature.
- Types or senses of torque: (i) Clockwise torque (ii) Anticlockwise torque.
- Definition of couple with explanation, unit example
- Definition of equilibrium with examples.
- Conditions of equilibrium first condition of equilibrium and second condition of equilibrium.
- Definition of first condition of equilibrium: mathematical form, and examples.
- Definition of Second condition of equilibrium: mathematical form, and examples.
- Definition of principle of moment: Mathematical form, and example.
- Types of equilibrium: (i) static equilibrium (ii) dynamic equilibrium.
- Definition of static equilibrium with examples.
- Definition of dynamic equilibrium with examples.
- The types of dynamic equilibrium: (i) dynamic transitional equilibrium (ii) dynamic rotational equilibrium.
- Definition of dynamic transitional equilibrium with examples.
- Definition of dynamic rotational equilibrium with examples.
- Definition of first stability and explanation.
- States of equilibrium: (i) stable equilibrium (ii) unstable equilibrium (iii) neutral equilibrium.
- Definition of stable equilibrium with examples.
- Definition of unstable equilibrium with examples.
- Definition of neutral equilibrium with examples.
- Can rectangular component of the vector can be greater than the vector itself? explain.
- Explain why door handles are not put near hinges?
- Can a small force ever exert a greater torque then a larger force? explain.
- Why it is better to use a long spanner than other than a short on the on to loosen a rusty nut?
- The gravitational force acting on a satellite is always directly towards the centre of the earth. Does this force exerted torque on satellite?
- Can we have suggestions in which an object is not in equilibrium, even though the net force on it is zero? give two examples.
- Why do tightrope walkers carry a long narrow rod?
- Why does a wearing high-heeled shoe sometimes the cause lower back pain?
- Why is it more difficult to learn backwards? explain.
- Can a single force applied to a body change both its translational and rotational motion? Explain.
- Two forces produce the same torque. Does it have follow them that they have the same magnitude? Explain. Describe the path of the brick after you shouldn't need to let go of the rope.
- Solved Numerical of the exercise Ch 4 Phy Class 9.
- To open a door force is 15N is applied at 30^o to the horizontal, find the horizontal and vertical components of force.
- Sana, who's mass is 43 kg, sits 1.8 m from the center of a seesaw. Faiz, who's mass is 52 kg, wants to balance Sana. How far from the center of the seesaw should Faiz sit?
- Two kids of weighing 300N and 350N sitting at the ends of 6 m long seesaw. The seesaw is pivoted at its center. Where would a third kid sit so that the seasaw in equilibrium in the horizontal position? The weight of the third kid is 250N. (Ignore the weight of see-saw).
- Two children push on opposite sides of a door during play. Both Push horizontally and perpendicular to the door. One child wishes with a force of 20N at a distance of 0.60 m from the hinges, and the secondary child pushes at a distance of 0.50 m. What force must the second child exert to keep the door from moving? Assume friction is negligible.
- A construction crane lifts building material of mass 1500 kg by moving its crane arm; Calculate moment of force when moment arm is 20 m. After lifting the crane arm, which reduces the moment are made to 12 m calculate moment.