Ch 4 Physics Class 9
Important easy to understand Notes of Ch 4 Physics Class 9 English Medium written by Professor Sulman Arif 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 Sindh Book Boards.
Summary and Contents:
Topics which are discussed in the notes are given below:
- Define like and unlike forces. Explain using examples.
- What is meant by resolution of forces? How the attraction and magnitude of a vector is obtained from its components?
- Which role is used to find the resultant of more than two forces. Give steps to add two vectors.
- Define resolution of vector. Derive expression for rectangular component of vector.
- Define torque. Give its formula and unit. Also, List the factors on which the moment of force depends.
- How is the sea-saw balanced?
- What is the centre of gravity? Give centre of gravity of some regular shape object.
- What is a couple? Write three necessary conditions for two forces to form a couple.
- Define equilibrium with example. Also, discuss its types: (i) Static equilibrium (ii) Dynamic equilibrium.
- State and explain condition of equilibrium: (i) First condition of equilibrium (ii) Second condition of equilibrium.
- what are the states of equilibrium. Also write their conditions: (i) Stable Equilibrium (ii) Unstable Equilibrium (iii) Neutral Equilibrium.
- Solved Numerical of the exercise Ch 4 Physics Class 9.
- A pair of like parallel forces 15N each are acting on a body. Find their resultant.
- A pair of like parallel forces 28N each are acting on a body. Find their resultant.
- A pair of like parallel forces 10N and 20N each are acting on a body. Find the resultant.
- A pair of like parallel forces 120N and 600N each are acting on a body. Find the resultant.
- Two unlike parallel forces 10N each acting along same line. Find the resultant.
- Two unlike parallel forces 9N each acting along same line. Find the resultant.
- Two unlike parallel forces with 13N and 10N each acting along same line. Find the resultant.
- A gardener is driving a lawnmower with a force of 80N that makes an angle of 40o with the ground. (I) Find its horizontal component. (ii) Find its vertical component.
- A gardener is driving a lawnmower with a force of 90N that makes an angle of 60o with the ground. (I) Find its horizontal component. (ii) Find its vertical component.
- Horizontal and vertical components of a force are 4N and 3N respectively. Find (i) Resultant Force (ii) Direction of Resultant.
- Horizontal and vertical components of a force are 8N and 6N respectively. Find (i) Resultant Force (ii) Direction of Resultant.
- A spanner of 0.3m in length can produce a torque of 300Nm. (i) Determine the force applied to it. (ii) What should be the length of spanner if torque is to be increased to 500Nm with the same applied force.
- A spanner of 0.5m in length can produce a torque of 450Nm. (i) Determine the force applied to it. (ii) What should be the length of spanner if torque is to be increased to 600Nm with the same applied force.
- A mechanic uses a double arm spinner to turn a net. He applies a force of 15N at each end of the spanner and produces a torque of 60Nm. What is the length of the moment arm of a couple? If he wants to produce a dark of 80Nm with the same spanner then how much force he should apply?