Download force and laws of motion - Indian School Al Wadi Al Kabir

INDIAN SCHOOL AL WADI AL KABIR
DEPARTMENT OF SCIENCE 2014 -15
CLASS IX
W.S. No.2
PHYSICS
Topic: FORCES AND LAWS OF MOTION
DATE: 17.08.14
Name:
Answer the following in one word or one sentence. Each question carries 1
mark
1. Give one point of difference between balanced and unbalanced forces.
2. State the law of conservation of momentum
Answer the following in about 30 words. Each question carries 2 marks.
3. Derive the Newton's first law of motion from the second law of motion.
[SA1 2013 ISWK]
2
4. A force of 10 N acts on m1 and m2 to accelerate them by 2m/s and 4 m/s2 if they are tied
together. Find the acceleration.
(Ans . 1.3 m/s2)
5. What is the principle behind the removal of dust from a carpet by beating it? Explain.
6. Name the principle behind the working of a rocket.Explain.
7. Any luggage kept on the roofs of cars or buses is always tied with a rope. Why?
8. (a) Write the relation between force and momentum
(b) It is difficult for a fireman to hold a hose, which ejects a large amount of water at a
high speed. Why?
Answer the following question in 50 words each. Each question carries
3marks each.
9. (a) Give the meaning of the term 'Inertia'.
(b) On what factor does the inertia of a body depend upon; explain with the help of a
suitable example.
10. Define momentum of a body. Write its SI unit. What is the relationship between force (F)
and acceleration (a) produced in a body of mass (m)? Find the acceleration produced by a
force of 25 N acting on a body of mass 5 kg.
(Ans =5 m/s2)
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11. A rifle of mass 3 kg fires a bullet of mass 0.03 kg.the bullet leaves the barrel of the rifle
at a velocity of 100 m/s.If the bullet takes 0.0035 seconds to move through its barrel,
calculate the force experienced by the rifle due to its recoil. Interpret the negative sign in
the answer.
(Ans. -85.7 N)
12. State the law of inertia. Why do we fall in the forward direction if a moving bus stops
suddenly and fall in the backward direction if it suddenly accelerates from rest?
13. A car starts from rest and moves down a hill with a constant acceleration. It travels a
distance of 300 m in 10 s. Find its acceleration. Find the force acing on it if its mass is
1500 kg. (Ans . a= 6m/s2, F=9000 N)
[SA1 2012 ISWK]
14. How would you arrive at a mathematical formula to measure force using Second law of
motion? Define the unit of force using this formula.
[SA1 2013 ISWK]
15. (a) A ball is allowed to roll down from an inclined plane. It reaches the foot of the plane
and continues to roll on the ground.it stops after travelling some distance.Is this the
violation of the law of inertia? Give reasons for your answer.
(b) A player lowers his hands while catching a ball. Explain reason behind this action.
[SA1 2013 ISWK]
Answer the following questions in about 70 words. The questions carry
5 marks
16. An engine exerts 5 N force opposing 2 N frictional force. How much distance will a car
of 1000 kg travel from the rest in 60 seconds ? (Ans =5.4 m)
[SA1 2013 ISWK]
17. The velocity time graph of a marble of mass = 10 g rolling along a straight line of a long
table is given below. After studying the graph, answer the questions given below
(a) What are the initial and final velocities of the marble?
(Ans u=10m/s and v=0m/s)
(b) Calculate its initial and final momentum.
(Ans P1=0.1 kgm/s,P2=0 kgm/s2)
10
(c) Find the acceleration of the marble and force exerted by the
v
table on the marble to bring it to rest
(Ans a= -1m/s2,F=-0.01 N) [SA1 2012 ISWK]
t
10
18. Define momentum.State its SI unit.An object of mass 50 kg is accelerated uniformly
from a velocity of 4 m/s to 8 m/s in 8 s.Calculate the initial and final momentum of the
object.Also find the force exerted on the object.
(Ans.P1=200 kgm/s,P2=400 kgm/s,F=25 N)
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Prepared by Ms. Jenesha J