Hello students, I hope you are preparing well for your respective examinations so for the same purpose we are here to provide you the best guidance as being your mentor and educator .In this article we have made the Class 9 Science Physics – Motion Chapter important Question Answers ,these all problems has been extracted from Motion Chapter based on equations of motion along with their detailed solutions. These are helpful for class 9–10 level students.
Equation of Motion Used:
Problem 1:
A car starts from rest and accelerates uniformly at 4 m/Sec2 . What is its velocity after 5 seconds?
Given: u= 0 , time T = 5 sec
Solution:
Using: V = u + a.t this formula
v = 0 + (4)(5) = 20 m/s
Answer: 20 m/sec
Problem 2:
A train moving with an initial velocity of 30 m is brought to rest by applying brakes. If the retardation is , find the distance it travels before stopping.
Solution:
Given: Final Velocity , V = 0 , initial velocity (u) = 30 m/sec ,
retardation ,a = -3 m/sec2
Using:
Answer: 150 m
Problem 3:
A body starts from rest and travels 80 m in 4 seconds under uniform acceleration. Find the acceleration.
Given: initial velocity , (u) = 0 ,
Time , t = 4 sec , distance (s) = 80 m
Using:
Solution:
Answer: 10 m/sec2
Problem 4:
A bullet moving at 200 m/sec and hits a wall and comes to rest in . Find the retardation.
Given:
initial velocity , (u) = 200 m/sec
Time , (t) = 0.01 sec
Using: V = u + a.t
Solution:
Answer: (retardation) , a = -20,000 m/sec2
Problem 5:
A car covers 100 m in 5 seconds with a uniform acceleration starting from . Find the acceleration.
Given:
Using: S = ut + ½ a.t2
Solution:
Answer: 4 m/sec2
Great! Here are 5 more problems on equations of motion with clear step-by-step solutions:
Problem 6:
A car accelerates from to in 4 seconds. Find the acceleration and the distance covered during this time.
Solution:
Given: t = 4 sec
Find out ; a = ? , d = ?
(i) Acceleration:
Using: formula V = U + a.t
25 = 15 + a(4)
a = {10}/{4} = 2.5 m/sec2
(ii) Distance covered:
Using:
s = 15(4) + {1}/{2}(2.5)(4^2) = 60 + {1}{2}(2.5)(16) = 60 + 20 = 80 m,
Answer: Acceleration = , Distance =
Problem 7:
An object moving with uniform acceleration travels 54 m in 3 seconds and 98 m in 5 seconds. Find the initial velocity and acceleration.
Given – distance = 54 m, Time t = 3 sec ,
Find out : initial velcoty , U = 0 , acceleration a = ?
Solution:
Let initial velocity and acceleration.
Using:
For 3 seconds:
→ Equation (1)
For 5 seconds:
→ Equation (2)
Now,
(1) →
(2) →
Multiply (1) by 5 and (2) by 3:
Subtract:
Substitute in (1):
Answer:
Problem 8:
A stone is dropped from a height of 80 m. How long will it take to reach the ground? (Take )
Solution:
Given:
Using:
80 = 0 + {1}{2}(9.8)t^2 , 80 = 4.9t^2 t^2 = \frac{80}{4.9} \approx 16.33 \Rightarrow t \approx 4.04 \, s
Answer:
Problem 9:
A vehicle moving at applies brakes and stops after 10 seconds. Find the distance it traveled after applying brakes.
Solution:
Given:
Using:
s = \frac{20 + 0}{2} \times 10 = 10 \times 10 = 100 \, m
Answer:
Problem 10:
A ball thrown vertically upwards reaches a maximum height of 45 m. Find the initial velocity. (Take )
Solution:
At max height, ,
,
Using: V2 = U2 + 2.a.s this formula (third equation of motion)
0 = u^2 + 2(-9.8)(45)
u^2 = 882 \Rightarrow u = \sqrt{882} \approx 29.7 \, m/s
Answer:
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