GRAVITATION CHAPTER # 06 PHYSICS 9TH – Short / Detailed Question Answers

 PHYSICS 9TH – Short / Detailed Question Answers

GRAVITATION
CHAPTER # 06
Q.1: State Newton’s Law of Gravitation. Derive the equation, $F = G\frac{m_1 m_2}{r^2}$.
Ans:
Newton’s Law of Gravitation:
Newton’s Law of universal gravitation states that: Every body in the universe attracts every other body with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.

FORCES AND MATTER Chapter #05 PHYSICS 9TH - Short / Detailed Question Answers

 PHYSICS 9TH - Short / Detailed Question Answers Chapter #05: FORCES AND MATTER

Q.1: What can a force do? Give some examples.
Ans:

1. Force is needed to move a car.
2. Force causes the spring to stretch.
3. We need force to move some luggage.
4. If we bend our plastic ruler, we will change its shape.
5. Force applied hands on the dough changes its shape.
6. A spring can be stretched or compressed by applying force.

TURNING EFFECT OF FORCES Chapter #04 PHYSICS 9TH - Short / Detailed Question Answers

 PHYSICS 9TH - Short / Detailed Question Answers

TURNING EFFECT OF FORCES

---

Q.1: Define force.

Ans: Force: Force is a push or pull which moves the objects. It can stop the objects. It also gives shape to the objects. It is a vector quantity. Therefore, it has a specific direction. It is measured in Newton (N).

Q.2: Define Parallel forces.

Ans: The parallel forces can be defined as, “when a number of forces act on a body and if their directions are parallel, they are called parallel forces.”

DYNAMICS CHAPTER # 03 PHYSICS 9TH – Short / Detailed Question Answers

 PHYSICS 9TH – Short / Detailed Question Answers

DYNAMICS
CHAPTER # 03

Q.1: Describe force and its unit.
Ans: Force:
Force is the agent that changes the state of rest or uniform motion of a body. Its S.I unit is Newton (N). One Newton (1N) is the amount of force that can produce $1 \, \text{ms}^{-2}$ acceleration in $1 \, \text{kg}$ mass. An object at rest needs a force to get moving; a moving object needs a force to come to rest or change its direction. The magnitude of a force can be measured using a spring balance.

In short, force is required to change the position, state, or shape of an object. It can act as a pull or push agent. Force produces acceleration and can produce distortion. It is a vector quantity.

KINEMATICS CHAPTER# 02 PHYSICS 9TH – Short / Detailed Question Answers

 PHYSICS 9TH – Short / Detailed Question Answers

KINEMATICS
CHAPTER# 02

Q.1: Define mechanics.
Ans: Mechanics:
The branch of physics which is related to the study of the motion of objects is called Mechanics. It is divided into two parts:
(i) Kinematics
(ii) Dynamics

MAGNETISM & ELECTROMAGNETISM

Chapter – 14

---

Q.1: What is flux density and how is it related to the number of lines of induction expressed in Webers?
Ans: Magnetic flux density $B$ is the magnetic flux per unit area $(B = \Phi / A)$. The unit of flux density is Weber per $m^2$ (or tesla, $T$). Magnetic flux is the total number of magnetic lines of induction passing perpendicularly through an area $(\Phi = B \times A)$. Its SI unit is ‘Weber’ $(1 Wb = 1 T \cdot m^2)$. Hence magnetic flux density refers to the number of lines of induction (in Webers) per square meter.

---

Q.2: Charged particles fired in a vacuum tube hit a fluorescent screen. Will it be possible to know whether they are positive or negative?
Ans: Yes, the charge on particles in motion can be found by applying a magnetic field perpendicular to the motion of the charges and by observing the deflection. A positive charge in an inward perpendicular magnetic field is deflected upward. In an electric field, a positive charge will be deflected towards the negative side (plate).

Physical Quantities and Measurement

 PHYSICS 9TH - Short / Detailed Question Answers

Q.1: What is Science?

Ans: Science:
The word science refers to the study of a fact by collecting information through observation, presenting it in a mathematical way, justifying the idea with experiment, and finally making a conclusion about the fact.

---

Q.2: Define Physics.

Ans: Physics:
One of the most basic and ancient sciences is Physics. It can be defined as: Physics is the branch of science which observes the nature, represents it mathematically, and concludes with the experiment.

In other words, Physics is the branch of science that deals with studies of matter, its composition, properties, and interaction with energy.