Class 9
Motion ( physics)
1. Define reference point.
Answer - A reference point is a place or an object used for comparison to determine if another object is
in motion or at rest.
2. Define scalar and vector quantities. Give examples.
Answer - A scalar quantity is defined as the physical quantities that has only magnitude.
Example: Mass, distance
A vector quantity is defined as the physical quantity that has both magnitude as well as direction.
Example: Displacement
3. What is distance? Write SI and CGS unit. Is it scalar or vector quantity?
Answer : The actual length of the path travelled by the object is known as distance. SI=m ,CGS= cm ,
scalar quantity.
4. What is displacement ? Write SI and CGS unit. Is it scalar or vector quantity?
Answer displacement is the shortest distance between initial and final position of the object. SI= m and
CGS =cm.
It has magnitude as well as direction, so displacement is a vector quantity.
5. Write two difference between distance and displacement.
Answer: Distance -i) The actual length of the path travelled by the object is known as distance.
ii) It is a scalar quantity.
iii) It cannot be zero, it is always positive.
Displacement - i) Displacement is the shortest distance between initial and final position of the object.
ii) It is a vector quantity.
iii)Displacement can be zero , positive and negative.
6. What instrument measures distance?
Answer : Odometer
, 7. Define speed. Write its SI and CGS unit.
Answer: Distance travelled by the object per unit time is known as speed. Speed = distance /time.
V = s/t.
SI = m/s , CGS = cm/s
8. Define average speed.
Answer: The average speed of an object is obtained by dividing the total distance travelled by the total
time taken.
Average speed = Total distance travelled / Total time taken.
9. Define uniform and nonuniform speed.
Answer : Uniform speed- An object is said to be in uniform speed when the object covers equal distance
in equal time intervals. Example: a car moving with the constant speed (25 m/s) for 15 minute.
Non uniform or variable speed: An object is said to be a non uniform or variable speed when the object
covers unequal distance in equal time intervals. Example: A bus moving on a crowded road.
10. What is the velocity ? Write its SI and CGS unit.
Answer: Velocity is defined as the rate of change of displacement of a body with respect to time. SI= m/s
, CGS = cm/s.
V=s / t, where V= velocity, S= displacement of a body.
11. Write two difference between speed and velocity.
Answer: Speed- i) Distance travelled by the body per unit time is known as speed.
ii) It is a scalar quantity.
iii) Speed of an object is always positive.
Velocity - i) Velocity is defined as the rate of change of displacement of a body with respect to
time.
ii) It is a vector quantity.
iii) Velocity of an object can be positive or negative.
12. What is motion?
Answer: A body is said to be in motion when it changes its position with respect to time and its
surroundings.
Motion ( physics)
1. Define reference point.
Answer - A reference point is a place or an object used for comparison to determine if another object is
in motion or at rest.
2. Define scalar and vector quantities. Give examples.
Answer - A scalar quantity is defined as the physical quantities that has only magnitude.
Example: Mass, distance
A vector quantity is defined as the physical quantity that has both magnitude as well as direction.
Example: Displacement
3. What is distance? Write SI and CGS unit. Is it scalar or vector quantity?
Answer : The actual length of the path travelled by the object is known as distance. SI=m ,CGS= cm ,
scalar quantity.
4. What is displacement ? Write SI and CGS unit. Is it scalar or vector quantity?
Answer displacement is the shortest distance between initial and final position of the object. SI= m and
CGS =cm.
It has magnitude as well as direction, so displacement is a vector quantity.
5. Write two difference between distance and displacement.
Answer: Distance -i) The actual length of the path travelled by the object is known as distance.
ii) It is a scalar quantity.
iii) It cannot be zero, it is always positive.
Displacement - i) Displacement is the shortest distance between initial and final position of the object.
ii) It is a vector quantity.
iii)Displacement can be zero , positive and negative.
6. What instrument measures distance?
Answer : Odometer
, 7. Define speed. Write its SI and CGS unit.
Answer: Distance travelled by the object per unit time is known as speed. Speed = distance /time.
V = s/t.
SI = m/s , CGS = cm/s
8. Define average speed.
Answer: The average speed of an object is obtained by dividing the total distance travelled by the total
time taken.
Average speed = Total distance travelled / Total time taken.
9. Define uniform and nonuniform speed.
Answer : Uniform speed- An object is said to be in uniform speed when the object covers equal distance
in equal time intervals. Example: a car moving with the constant speed (25 m/s) for 15 minute.
Non uniform or variable speed: An object is said to be a non uniform or variable speed when the object
covers unequal distance in equal time intervals. Example: A bus moving on a crowded road.
10. What is the velocity ? Write its SI and CGS unit.
Answer: Velocity is defined as the rate of change of displacement of a body with respect to time. SI= m/s
, CGS = cm/s.
V=s / t, where V= velocity, S= displacement of a body.
11. Write two difference between speed and velocity.
Answer: Speed- i) Distance travelled by the body per unit time is known as speed.
ii) It is a scalar quantity.
iii) Speed of an object is always positive.
Velocity - i) Velocity is defined as the rate of change of displacement of a body with respect to
time.
ii) It is a vector quantity.
iii) Velocity of an object can be positive or negative.
12. What is motion?
Answer: A body is said to be in motion when it changes its position with respect to time and its
surroundings.
