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Syllabus

Q). In Fig. 1.34, a uniform bar of length l m is supported at its ends and loaded by a weight W kgf at its middle. In equilibrium, find the reactions ${R}_{1}and{R}_{2}$ at the ends.

Q(b) (i). Diagram alongside shows a nut cracker with a wooden base. If the effort required to crack the nut is 50 N, find the resistance offered by the nut.

(ii) What force should be directly applied on the nut , so as to crack it without the help of nut cracker ?

question 16

a uniform metre scale is balanced at 60 cm mark , when weight of 5 gf and 40 gf are suspended at 10 cm mark and 80 cm mark respectively calulate the weight of the metre saclea uniform metre scale is balanced at 20 cm mrk when a weight of 100 gf is suspended from the end where must the weight be suspended calculate the weight of the metre saclea uniform metre sacle balances horizontally on aknife edge placed mass of 25 g is supported from one end draw the diagram of the arrangement calculate mass of the scale .Q9. A block A, weighing 100 N, is pulled up a slope of length 5 m by means of a constant force F (= 100 N) as illustrated in Fig. 2.15.

(a) What is the work done by the force F in moving the block A, 5 m along the slope?

(b) What is the increase in potential energy of the block A ?

(c) Account for the difference in the work done by the force and the increase in potential energy of the block.

Q.5. A sign weighing 98 N is suspended from the middle of a 4 m long chain. The ends of the chain are attached to a ceiling at points 3 m apart. Determine the tensions in the chains.

Q.18. A uniform metre scale is balanced at 40 cm mark, when weights of 20 gf and 5 gf are suspended at 5 cm mark and 75 cm mark respectively. Calculate the weight of metre scale.

[Ans. 52.5 gf]

Q.16. In fig. if the surfaces are frictionless the ratio ${T}_{1}:{T}_{2}$ is -

(1) $\sqrt{3}$ : 2

(2) 1 : $\sqrt{3}$

(3) 1 : 5

(4) 5 : 1

16. A boy takes 3 minutes to lift a 20 litre water bucket from a 20 m deep well, while his father does it in 2 minutes. (a) Compare : (i) the work, and (ii) power developed by them. (b) How much work each does ? Take density of water = 10

^{3}kg ${m}^{-3}$ and g = 9.8 N k${g}^{-1}$.Ans. (a) (i) work 1 : 1, (ii) power 2 : 3, (b) work done by each = 3.92 kJ

Q.(b) A ball of mass 15 g is thrown vertically upwards with initial velocity of 20 $m{s}^{-1}$ At what height above the ground the ball would have equal potential and kinetic energy? [Take g = 10 $m{s}^{-2}$]

Question l.

(a) A brass ball is hanging from a stiff cotton thread. Draw a neat labelled diagram showing the forces acting on the brass ball and the cotton thread.

(b) The distance between two bodies is doubled. How is the magnitude of gravitational force between them affected?

Question: what is the average of all these distances?

That is to say, what is the time average of the distance traveled?

Q.15. Explain the following:

(a) Why is it easier to pull down the branch of a tree from its free end than from anywhere else?

(b) Why do we use a long handle with a screw jack?

(c) Why do we use a long spanner to open a tight nut?

(d) Why is the upper stone of a hand flour grinder provided with a handle near its rim?

Q26. (a) (i) When does a force do work?

(ii) What is the work done by the moon when it revolves around the earth?

(b) Calculate the change in kinetic energy of a moving body, if its velocity reduced to $\frac{1}{3}$of the initial velocity.

$\left[\frac{4}{9}\right]$

(c) State the energy change in the following devices while in use:

Q(c). The diagram below shows a lever in use:

(i) To which class of levers does it belong ?

(ii) Without changing the dimensions of the lever, if the load is shifted towards the fulcrum what happens to the mechanical advantage of the lever ?

5.The wheel shown in the diagram (Fig. 1.17) has a fixed axle passing through O. The wheel is kept stationary under the action of (i) a horizontal force F_{1}at A and (ii) a vertical force F_{2}at B.(b) Which of the force F

_{1}or F_{2}is greater ?Q.16. The adjacent diagram (Fig. 1.27) shows a heavy roller, with its axle at O, which is to be raised on a pavement XY. If there is friction between the roller and pavement, show by an arrow on the diagram the point of application and the direction of force to be applied.

Please do not provide any link.

Q.(e). A metal ball of mass 60 g falls on a concrete floor from a vertical of 2.8 m and rebounds to a height of 1.3 m. Find the change in K.E. in S.I. units.

(a) useful force exerted by the engine in newton.

[Ans. 750 N]

(b) power developed in kilowatt at 54 km/h

Assume that all frictional forces are absent.

[Ans. 11.25 kW]

(a) Zero (b) 4 mg (c) 5 mg (d) 1 mg.

9. A block and tackle system has the velocity ratio 3. Draw a labelled diagram of the system indicating the points of application and the directions of load and effort. A man can exert a pull of 200 kgf. What is the maximum load he can raise with this pulley system if its efficiency is 60%?

Ans : 360 kgf

PS : Sir PLEASE explain each step because I didn't understand all the steps in a solution given for this same sum earlier.PLEASE DONT GIVE A LINK TO A SIMILAR ANSWER .....Thanks

a uniform metre scale of weight 50 gf is balanced at the 40 cm mark when a weight of 100 gf is suspended at the 5 cm mark where of 80 gf be suspended to balanced the metre sacle ?a sees-saw 8 m long is balanced in the middle two children of mass 30 kgf and 40 kgf are sitting on the same side of the fulcrum at a distance of 1.5 m and 35 m from the fulcrum respecitvely where must a lady weighing 60 kgf sit from the fulcrum so as to blance the see- saw ?Q. A cubical block of side 10 cm floats at the interface of an oil and water. The pressure above that of atmosphere at the lower face of the block is

21.. Momentum is directly proportional to

(a) Acceleration (b) Mass

(c) Force (d) Speed.

1. THE RATIO OF AMPLITUDES OF Two WAVES IS 3.4 .WHAT IS THE RATIO OF THEIR:

a) loudness b) frequencies

2. STATE Two WAYS IN WHICH THE FREQUENCY OF TRANSVERSE VIBRATIONS OF A STRETCHED STRING CAN BE INCREASED?

3. WHAT IS MEANT BY NOISE POLLUTION? NAME ONE SOURCE OF SOUND CAUSING NOISE POLLUTION?

4. A STONE OF MASS m IS ROTATED IN A CIRCULAR PATH WITH A UNIFORM SPEED BY TYING A STRONG STRING WITH THE HELP OF YOUR HAND ANSWER THE FOLLOWING QUESTIONS:

a)is the Stone moving in uniform or variable speed?

b)is the stone moving with uniform acceleration?in which direction does the acceleration act?

c) what kind of forces act on the Stone and also state its direction.

5. a)WHAT AN ECHO? (3)

b).STATE TWO CONDITIONS FOR AN ECHO TO TAKE PLACE.

6. a)NAME THE PHENOMENON INVOLVED IN TUNING A RADIO SET TO A PARTICULAR

B) DEFINE THE PHENOMENON NAMED BY you IN PART A ABOVE.

C) WHAT DO you UNDERSTAND BY LOUDNESS OF SOUND?

D) WHICH uNlTS IS THE LOUDNESS OF SOUND MEASURED?

7. DEFINE THE UNIT OF FORCE.

8. WHAT ARE THE TWO CONDITIONS THAT MUST BE SATISFIED FOR A BODY TO BE IN

9. DEFINE MOMENT OF FORCE AND STATE ITS SI UNIT.

10 A UNIFORM BAR IS SUPPORTED AT THE MIDDLE POINT BY A FULCRUM A WEIGHT OF 40 GF IS PLACED AT A POINT OF 40 CM TO THE LEFT OF THE FULCRUM.HOW CAN you BALANCE THE BAR WITH A WEIGHT OF 80 GF?

11. A UNIFORM METRE RULE OF MASS 100 G IS BALANCED ON A FULCRUM AT 40 CM MARK BY SUSPENDING AN UNKNOWN MASS "L" AT THE 20 CM MARK.

i)find the value of "L"

ii)to which side will the rue tilt if the mass "L" is moved to mark 10 cm?

iii)what is the resultant moment now?

iv)how can it be balanced by another mass of 50 g?

12. WHAT THE POSITION OF CENTRE OF GRAVITY OF A i)solid cone ii)triangular lamina.

13. WHAT DO you MEAN BY SUBJECTIVE NATURE OF LOUDNESS AND OBJECTIVE NATURE OF INTENSITY?

14. STATE TWO FACTORS AFFECTING THE LOUDNESS OF A SOUND AND ALSO STATE HOW DOES IT DEPENDS?

15. WHEN A TROOP CROSSES A SUSPENSION BRIDGE THE SOLDIERS ARE ASKED TO BREAKS STEPS. WHY?

Q5. The wheel shown in the diagram (Fig. 1.17) has a fixed axle passing through O. The wheel is kept stationary under the action of (i) a horizontal force F

_{1}at A and (ii) a vertical force F_{2}at B.(a) Show the direction of force F

_{2}_{ }in the diagram.(b) Which of the force F

_{1}or F_{2}_{ }is greater?(c) Find the ratio between the forces F

_{1}and F_{2}. Given : AO = 2.5 cm, BO' = 1.5 cm and O'O = 2.0 cm.If yes, which class does it belong

If no, why?

Justify answer giving proper reasons

20.A small plane with a mass of 1200 kg cruises at 140 km h^{$-$1}at an altitude of 1.5 km. Taking g = 10 ms

^{$-$2}, calculate its:(a) potential energy and

[Ans. 1.8 $\times $ 10^{7}J](b) kinetic energy

[Ans. 9.074 $\times $ 10^{5}J]