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1. Class 9th Physics
Chapter#2, Kinematics
Problem #2.5-2.7
By: Muhammad Zeeshan
Easy learning

2. Data: vi=40m/s, t1 =5s, t2=10s, vf=0
Find: a=? S=?
Formula: For a vf=vi+at2
0= 40+(a)(10) ⟹ -40=10a
a=-40/10=-4m/s2
Now, For total distance S=S1 + S2
S1=vt1
S1= 40×5=200m
S=S1+S2=200+200=400m
P#2.5. A car moving with uniform velocity of 40m/s for
5 sec. It comes to the rest in next 10s with uniform
deceleration. Find i. deceleration ii. Total distance
travelled by the car.
According to
condition time t2 =10 s
for declaration
S1= distance in time t1
S2= distance in time t2
− Sign show deceleration
S2 = Vit2 +1/2at2
2
S2=40 10 +
1
2
(−4)(100)= 400-200=200m

3. Data: vi = 0m/s , a=0.5m/s2, S=100m
Find: vf=?
Formula: 2as=vf
2-vi
2 ⟹ vf
2=2as + vi
2
vf
2= 2(0.5)(100) + (0)2
vf
2=2(1/2)(100)
vf
2=100(m/s)2
vf=10m/s
vf=
10×3600
1000
𝑘𝑚ℎ−1
vf=36 𝑘𝑚ℎ−1
P#2.6. A train start from a rest with an acceleration of
0.5m/s2 . Find its speed in Km/h, when it has moved
through 100m.
1km
÷ ×
1000m
1h
÷ ×
3600s

4. Find: S=?
The distance divided into three interval of time so total distance S=S1+S2+S3
1. A train starting from rest accelerates uniformly and attains a velocity 48
kmh-1 in two minutes
Data: vi=0, vf=48km/h=
48000
3600
m/s=
40𝑚
3𝑠
, t1= 2min=2× 60𝑠=120s ,Find: S1=?
Formula: For S1, 2aS1=vf
2-vi
2 ⟹ 𝑆1 =
𝑣 𝑓
2−𝑣 𝑖
2
2𝑎
, a=
(𝑣 𝑓−𝑣 𝑖)
𝑡
a=
40
3
−0
120
=
40
3
×
1
120
=
1
9
= 0.111𝑚𝑠−2
Now, S1=
(
40
3
)2−02
2(0.111)
=
1600
9
×
1
0.222
= 800𝑚
P#2.7. A train starting from rest, accelerates uniformly and
attains a velocity 48 kmh-1 in 2 minutes. It travels at this
speed of 5 minutes. Finally, it moves with uniform
retardation and is stopped after 3 minutes. Find the total
distance travelled by the train.

5. 2. It travels at this speed for 5 minutes.
Data: vf = vi = vav = 40/3 ms-1, t = 5min = 5×60 = 300s Find: S2=?
Formula: S= vavt
Putting the values S2 = 40/3 ms-1 × 300s =4000m
3. Finally it movies with uniform retardation and It stopped after 3
minutes.
Data: vi = 40/3 ms-1, vf = 0 ms-1, t = 3min = 3×60 = 180s, Find: S3=?
Formula: 𝑆 = 𝑣 𝑎𝑣𝑒 × 𝑡 , 𝑣 𝑎𝑣𝑒=
vf +vi
2
𝑆3 =
40
3
+ 0
2
× 180 =
40
3
× 90 = 40 × 45 = 1200𝑚
Total Distance
Total distance = S1 + S2 + S3
Total distance = 4000m+800m+1200m
Total distance = 6000m.