CLASS-9 SUBJECT SCIENCE CHAPTER-8 MOTION

 EVENTS CONVENT HIGH SCHOOL

01/02/2022      CLASS- 9   SESSION 2021-22
SUBJECT : SCIENCE

CHAPTER-8
MOTION

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Very Short Answer Questions

Question 1.The phenomenon of motion was placed on a sound scientific footing by two scientists. Write their names.
Answer:
Galileo Galilei and Isaac Newton.

Question 2.Are rest and motion absolute or relative terms?
Answer:
They are relative terms.

Question 3.Suppose a ball is thrown vertically upwards from a position P above the ground. It rises to the highest point Q and returns to the same point P. What is the net displacement and distance travelled by the ball?
Answer:
Displacement is zero. Distance is twice the distance between position P and Q.

Question 4.Which speed is greater: 30 m/s or 30 km/h?
Answer:
30 m/s

Question 5.What do you mean by 2 m/s2?
Answer:
The velocity of the body increases by 2 m/s after every second.

Question 6.Can uniform linear motion be accelerated?
Answer:
No

Question 7.Define one radian.
Answer:
It is the angle which is subtended at the centre by an arc having a length equal to the radius of the circle.

Question 8.What is the relation between linear velocity and angular velocity?
Answer:
Linear velocity = Angular velocity × Radius of circular path.

Short Answer Type 1

Question 1.Distinguish between speed and velocity.
Answer:
Speed:

• Speed is the ratio of distance and time.
• Speed is always positive
• Speed is a scalar quantity.

Velocity:

• Velocity is the ratio of displacement and time.
• Velocity may be negative or positive.
• Velocity is a vector quantity.

Question 2.Distinguish between distance and displacement.
Answer:
Distance

• It is the actual length of the path covered by a moving body.
• It is always positive or zero.
• It is a scalar quantity.

Displacement:

• It is the shortest distance measured between the initial and final positions.
• It may be positive, negative, or zero.
• it is a vector quantity.

Question 3.Write down the SI unit of the following quantities:
(a) Displacement
(b) Speed
(c) Velocity
(d) Acceleration
Answer:
(a) m
(b) m/s
(c) m/s
(d) m/s2

DEFINE

Question 1.Define the following terms:
(a) Distance
(b) Displacement
(c) Speed
(d) Velocity
(e) Acceleration
(f) Uniform motion
(g) Uniform circular motion
(h) Scalar quantity
(i) Vector quantity

Answer:
(a) Distance: The total path length traveled by a body in a given interval of time is called distance.
(b) Displacement: The shortest distance measured from the initial to the final position of an object is known as displacement.
(c) Speed: The speed of a body is defined as the distance traveled per unit time.
(d) Velocity: Velocity is defined as displacement per unit time.
(e) Acceleration: The rate of change of velocity with respect to time.
(f) Uniform motion: A body moving in a straight line has a uniform motion if it travels the equal distance in equal intervals of tune.
(g) Non-uniform motion: A body has a non-uniform motion if it travels unequal distances in equal intervals of time.
(h) Scalar quantity: A physical quantity which is described completely by its magnitude only, is called a scalar quantity.
(i) Vector quantity: A physical quantity that has magnitude as well as direction and obeys the vector addition is called a vector quantity.

Question 2.Draw a position-time graph of for
(a) rest
(b) uniform motion
(c) Non-uniform motion
Answer:
(a) Position – time graph for rest

(b) Position – time graph for uniform motion

(c) Position – time graph for non-uniform motion