9th standard syllabus notes and 30 questions on the content attached

1. Motion 1

2. Uniform motion
▪ When an object covers equal distances in equal
intervals of time, it is said to be in uniform motion.

3. Non-Uniform Motion
▪ When an object covers unequal distances in equal
intervals of time, for example, when a car is
moving on a crowded street or a person is jogging
in a park.These are some instances of non-uniform
motion.

4. Speed
▪ Definition: Speed is the distance travelled by the
object in unit time.
▪ SI unit: metre per second (m s–1 or m/s)
▪ Formula: Average speed= Total distance travelled
/Total time taken.

5. Velocity
▪ Definition:Velocity is the speed of an object
moving in a definite direction.The velocity of an
object can be uniform or variable. It can be changed
by changing the object’s speed, direction of motion
or both.
▪ SI unit: metre per second (m s–1 or m/s)
▪ Formula: Average velocity = initial velocity +final
velocity/2

6. Rate of Change of Velocity
▪ During uniform motion of an object along a
straight line, the velocity remains constant with
time. Rate of change of velocity is zero.
▪ In non-uniform motion, velocity varies with time.
Hence the change in velocity of the object during
any time interval is not zero.

7. Acceleration
▪ Definition: It is a measure of the change in the
velocity of an object per unit time.
▪ Formula: Acceleration = change in velocity/ time
taken.
▪ A= v-u/t where v= Final velocity, u= Initial velocity.
▪ SI unit: m s–2

8. Uniform and non-uniform acceleration
▪ Uniform acceleration: If an object travels in a
straight line and its velocity increases or decreases
by equal amounts in equal intervals of time.
▪ Non-Uniform acceleration:Velocity changes at a
non-uniform rate. Increases its speed by unequal
amounts in equal intervals of time.

9. Distance time graph
▪ The change in the position of an object with time
can be represented on the distance-time graph.
▪ Time is taken along the x–axis and distance is
taken along the y-axis.

10. Graph of uniform motion
To determine Speed
from the distance-time
graph.
V= S2-S1
T2-T1

11. Graph of non-uniform motion
The nature of this graph
shows nonlinear variation
of the distance travelled
by the car with time.

12. 1. How do you describe motion?
A. We describe the location of an object by specifying a reference
point.
2.What is a reference point?
A. A school in a village is 2 km north of the railway station. We have
specified the position of the school with respect to the railway
station. In this example, the railway station is the reference point.
3.What is the distance and displacement inn this case shown below if
objects moves from O to A and comes back fromA to C
A. Distance = 85 km
B. Displacement = 25 km

13. 4.What is displacement?
A. Displacement, are used to describe the overall motion of an object
and to locate its final position with reference to its initial position
at a given time.
5. Can the magnitude of displacement be greater than distance?
A. No it is not possible. It can be less but not more.
6. Can the displacement of an object be zero. How can it be?
A. When an object moves from initial position to another position
and then returns back to its initial position then its displacement
becomes zero because the change in position from initial to final is
zero here so the displacement also becomes zero.
7.What is uniform motion?
A.When an object covers equal distances in equal intervals of time, it
is said to be in uniform motion.

14. 8.What is non-uniform motion?
A. When an object covers unequal distances in equal intervals of
time, for example, when a car is moving on a crowded street or a
person is jogging in a park.These are some instances of non-
uniform motion.
9.What is speed?
A. Speed is the distance travelled by the object in unit time.
10. How do you calculate speed?
A. Formula: speed= distance travelled / time taken.
11.What are various units of speed?
A. The SI unit of speed is metre per second.This is represented by the
symbol m s–1 or m/s.The other units of speed include centimetre
per second (cm s–1) and kilometre per hour (km h–1).

15. 12.What is average speed?
A. The average speed of an object is obtained by dividing the total
distance travelled by the total time taken.This is calculated when
the speed is not constant.
Average speed= Total distance travelled /Total time taken.
13.What do you understand if 30km/hr is the average speed of a
body?
A. Its average speed is 30 km h–1.The car might not have travelled
at 30 km h–1 all the time. Sometimes it might have travelled
faster and sometimes slower than this.
14. An object travels 10 m in 4 s and then another 15 m in 2 s. What is
the average speed of the object?
A. Total distance= 10+15= 25
Total time= 6
Av speed= 25/6= 4.16m s–1

16. 15.What is speed with direction?
A. The rate of motion of an object can be more comprehensive if we
specify its direction of motion along with its speed.The quantity
that specifies both these aspects is called velocity.
16. Define velocity
A. Velocity is the speed of an object moving in a definite direction.
The velocity of an object can be uniform or variable. It can be
changed by changing the object’s speed, direction of motion or
both.
17.The odometer of a car reads 2000 km at the start of a trip and
2500 km at the end of the trip. If the trip took 8 h, calculate the
average speed of the car in km h–1 and m s–1.
A. Av speed= 500/8= 62.5km/hr
In meters/second= 17.36m/s

17. 18.Trisha swims in a 50 m long pool. She covers 100 m in one minute
by swimming from one end to the other and back along the same
straight path. Find the average speed and average velocity of Usha.
A. Average speed=100/60= 1.667m/s
Average velocity = 0 since displacement is 0
19. Explain uniform motion int erms of velocity.
A. During uniform motion of an object along a straight line, the
velocity remains constant with time. Rate of change of velocity is
zero.
20.What is acceleration?
A. It is a measure of the change in the velocity of an object per unit
time.

18. 21.What is uniform acceleration.
A. Uniform acceleration: If an object travels in a straight line and its
velocity increases or decreases by equal amounts in equal
intervals of time.
22.What is non-uniform acceleration?
A. Non-Uniform acceleration:Velocity changes at a non-uniform
rate. Increases its speed by unequal amounts in equal intervals of
time.
23.What is a distance time graph
A.The change in the position of an object with time can be
represented on the distance-time graph.
Time is taken along the x–axis and distance is taken along the y-axis.

19. 24. Calculate the acceleration of a body when its initial velocity is 30
m/s and final velocity is 100m/s.The change in velocity occurs in 10s.
A. a=v-u/t= 100-30/10= 7m/s2
25. Show the graph of a uniform motion.
A.
26. Identify the graph shown in the diagram
A. Distance time graph – Uniform motion

20. 27. Find the distance in this case where AB= 10 and BC= 5
A. s= area=bh= 5x10= 50m
28. Find velocity from the given graph where t2=4s, t1= 1s, s2= 40m,
s1=10m
A.
v= s2-s1= 40-10/4-1= 30/3= 10m/s
t2-t1

21. 29. From the table say whether it is uniform or non-uniform motion
A. Uniform motion
30. From the table say whether uniform or non-uniform motion.
A. Non-uniform motion
Time (in s) Distance (in m)
0 0
2 5
4 10
6 15
8 20
Time (in s) Distance (in m)
0 0
2 5
4 17
6 23
8 28