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HomeExam TipsEXAM TIPS : PHYSICS 9th CLASS

# EXAM TIPS : PHYSICS 9th CLASS

1. Using the relation in the first word pair complete the second.

Hydraulic brake                  :    Pascal’s Law

Hydrometer                        :    ……………….

1. Which among the following does not show capillary rise?

(Water, Kerosene, Mercury, Saline water)

1. The velocity – time graph of a moving body is a straight line parallel to the X axis. Which of the following is the most suitable in respect of its motion.(Non uniform speed, Non uniform velocity,

Uniform velocity, Non uniform acceleration)

1. The force required to produce an acceleration of 1 m/s2 on a body of mass 1 kg is…..
2. According to Newton’s First law of motion an unbalanced force is required to change the state of rest of a body.

(a)  What do you understand by the term ‘unbalanced force’?

(b) In addition to this the force should have another peculiarity also. What is that?

1. A body in motion does not need an unbalanced external force to continue in its state of uniform motion along a straight line.

(a)  Who explained this concept on the basis of experiments followed by accurate observations.

(b) A ball rolling through a level ground comes to rest after some time. Identify the unbalanced external force acted on the body which makes the body comes to rest.

1. An iron block and an aluminium block of same mass are immersing in a liquid.

(a)  Which one experiences more buoyancy?

(b) Which factor that influence buoyancy is responsible for this?

(c)  Which quality of the liquid is the next factor that influence buoyancy?

1. Tabulate the following according to their ability to flow. Give suitable title to each.

Honey, Kerosene, Petrol, Water, Glycerin, Caster oil, Ghee, Spirit.

1. The body of a person who got electric shock is to be massaged continuously. What is the reason for this?
2. Classify the following as those related inertia of motion and those related to inertia of rest in a table.

(a)  The athletes take a short run before having a long jump.

(b) The dust particles in a carpet can be removed by striking it with a stick.

(c)  When a man is chased by an elephant, he should take a zig-zag path.

(d) When the branch of a mango tree is shaken, mangoes fall just as when the branch starts moving.

(e) When a bus starts moving suddenly the standing passengers tend to fall backward.

(f)  Accidents that happen to passengers who do not wear seat belts are more fatal.

1. A car having a mass of 800 kg is moving with a velocity of 15 m/s. Brake is applied and the car is brought to rest in 3s.

(a)  Calculate the acceleration experienced by the car.

(b) What do we call such acceleration?

(c)  Find the distance travelled by the car after applying brake.

(d) Calculate the force applied to stop the car.

1. Match the following correctly.
 Decreases on adding soap (i) Buoyancy (a) Greater Adhesion (p) Loss of weight of the body (ii) Relative density (b) Cohesion (q) Lactometer (iii) Water (c) Weight of water displaced (r) Capillary rise (iv) Surface tension (d) Hydro meter (s)

13 (a)State the law relating rate of change of momentum and force applied.

(b) Using this law derive an equation to measure force.

1. Find the factors responsible for the following.

(a)  A ship entering sea from a lake raise up a little.

(b) Water from soil reaches the leaves.

(c)  A wet paper can stick on a wall.

(d) The bristles of a shaving brush  cling together after dipping in water.

1. A small metallic ball from the top of a tower reaches the ground in 2s.

(a)  Find the height of the tower (a=10 m/s2)

(b) Derive the third equation of motion using the given graph.

1. Principle of floatation
2. Mercury
3. Uniform velocity
4. 1 N
5. (a)If the resultant of all forces acting on body is zero, then the applied forces are said to be unbalanced.

(b) The force should be external

6    (a)  Galileo

(b) Frictional force

7(a)     Aluminium block

(b) Volume of the body immersed. Here the masses of iron block and the aluminium block are the same. But iron is denser than aluminium. So the volume of Aluminium block is greater than that of iron block.

(c)  Density of liquids.

 Viscous liquid Mobile liquid Honey Glycerin Ghee Caster oil Kerosene Petrol Water Spirit

1. When a person receives electric shock his body temperature falls suddenly. Thus the viscosity of the blood suddenly decreases and begins to clot. To avoid this his body is to massaged continuously.

10.

 Inertia of motion Inertia of rest a d f b c e

1. m = 800 kg u = 15 m/s v = 0  t = 3s

(a)

(b)Retardation

(c) s = ut +  at2 = 15 ´ 3 +  ´ (-5) x 3 x 3

= 22.5 m

(d) F = ma

F = 800 x -5 = -4000 N

12 i     –     d    –      q

ii    –    a    –      r

iii   –    b    –      s

iv   –    c    –      p

1. (a) Newton’s second law of motion. The rate of change of momentum of a body is directly proportion to the unbalanced external force acting on it.

(b) A body of mass ‘m’ is moving with a velocity ‘u’. A force ‘F’ acts for a time of ‘t’ seconds and the velocity changes to v

Initial momentum P1        =  mu

Final momentum P2 =      mv

Change of momentum

= P2 – P1 = mv – mu = m(v-u)

Rate of change of momentum=  = ma

According to Newton’s Second law

Force µ Rate of change of momentum

F µ ma

the value of k = 1 F = kma,

F = ma

1. (a)Density of sea water is more than lake water. So buoyancy of sea water increases and the ship raises.

(b) Capillarity

(c)  Adhesion between paper, water and wall

(d) surface tension

1. u = 0, t = 2s,   a = 10 m/s2

(a) s = ut + at2

= 0 ´ 2 +  ´ 10 ´ 2 ´ 2 = 20m

(b)From the graph

Displacement = Area of the trapezium

s = ´t´(u+v) ……….(1)

But a =

Substitute this value of a in equation (1) we get

2as = v2 – u2;                       v2 = u2 + 2as