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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 801. |
A man fires a gun and hears its echo after 5s. The man then moves 310 m towards the hill and fires his gun again. If he hears the echo after 3 s, calculate the speed of sound. |
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Answer» SOLUTION :Distance (d) = VELOCITY (v) `xx` time (t) Distance TRAVELLED by sound when gun fires FIRST time, `2d=v xx 5 "" ………..(1)` Distance travelled by sound when gun fires second time, `2d-620=v xx 3 ""…………..(2)` Rewriting equation (2) as, `2d=(v xx 3)+620""............(3)` Equating (1) and (3), `5v=3v+620` `2v=620` Velocity of sound, `v=310 m s^(-1)` |
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| 802. |
Kerosene and saline water are taken in two beakers. The same stone is immersed in both liquids. Write whether the buoyancy of that liquid is more or less than that of the other liquid? |
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| 803. |
Rohan is a student of class iX in a city school. Rohan visited his ancestral village alongwith his grandmother during the summer holidays. One day a Baba came to the village and told the villagers that he can perform a miracle by lying down on a bed of nails. So, a bed having thousands of nails was made for him. when all the village people had gathered, Baba recited a few mantras loudly and lay down on the bed of nails very, very carefully. The high poing og this so called miracle was that Baba was not hurt at all by the large number of nails below his body. All the village people were highly impressed by this miracle of Baba. Even Rohan's grandmother was greatly impressed by this feat. But Rohan, who studies science, was not impressed at all. In fact, Rohan told the gathered village people that it was no miracle. This feat of Baba was based on a well known scientific principle. He told the people that any person can lie on a bead of of nails unhurt, if there is a very large number of nails. Even he could lie on the same bed of nails without being hurt. He explained the underlying scientific principle to all the people. Even Baba was surprised by the knowledge of a school boy like Rohan. (a) Which concept of science is involved in the show put by Baba by lying down o a bed of nails? (b) Define and explain the above concept. (c) What happens if we step barefooted on a nail accidently? Explain. (d) Why did Baba not get hurt by lying down on a bed of nails? Explain. (e) What values are displayed by Rohan? |
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Answer» Solution :(a) The concept of science involved in the show put by Baba is that of pressure. (b) Pressure is the force acting on a unit area of an object. The same force can produce different pressures depending on the size of the area over which it acts. For example: (i) When a force acts on a small area of an object, it produces a large pressure. (ii) But when the same force acts over a large area of the object, then it produces a small pressure. (c) If we step barefooted on a nail accidently, then our foot gets hurt badly. This is because then the force of our entire body WEIGHT falls on the extremely small area of the tip of a single nail making the pressure extremely large. It is this extremely large pressure on a single nail which can pierce our foot and hurt the food badly. (d) The bed of nails has THOUSANDS of nails close to one another. When the Baba LIES down on the bed of thousands of nails then the force of this body weight gets distributed over the large area of thousands of nails. Due to this, the net pressure on a single nail becomes very small and hence the Baba's body does not GET hurt at all. (e) The various values displayed by Rohan are (i) Knowledge of the concept of pressure (ii) Application of knowledge in everyday situations, and (III) Desire to remove the myth (false belief) of miracles from the minds of village people. |
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| 804. |
A book of mass 1 kg is raised through a height .h.. If the potential energy increased by 49 J, find the height raised. |
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Answer» Solution :The increase in POTENTIAL energy = MGH That is , mgh = 49 J (1) (9.8)h = 49 J The height RAISED, `h = (49) //(1xx9.8)` = 5m |
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| 805. |
A particle initially at rest, moves with an acceleration 5 m s^(-2) for 5 s. Find the distance travelled in (a) 4 s, (b) 5 s and (c) 5th second. |
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Answer» Solution :Given initial velocity U =0 acceleration a= 5 `m s^(-2)` (a) Distance travelled in t =4 s, `S_(1) =ut +(1)/(2) at^(2) =0xx4 +(1)/(2) xx5 xx(4)^(2)` = 40 m (b) Distance travelled in t = 5 s , `S_(2) = ut +(1)/(2) at^(2) = 0 xx5 +(1)/(2) xx5 xx(5)^(2)` = 62.5 m (c ) Distance travelled in `5^(th)` second , = Distance travelled in 5 s - Distance travelled in 4 s = `S_(2) - S_(1) = (62.5 -40) m = 22.5 m` |
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| 806. |
A particle is moving on a circle of radius r. The displacement at the end of half revolution would be … |
Answer» SOLUTION :
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| 807. |
An observer sitting in line of two tanks, watches the flashes of two tanks firing at each other at the same time, but he hears the sounds of two shots 2 s and 3.5 s after seeing the flashes. If distance between the two tanks is 510 m, find the speed of sound. |
| Answer» SOLUTION :`340 MS^(-1)` | |
| 808. |
The global warming has resulted in |
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Answer» the INCREASE in YIELD of crops |
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| 809. |
A hockey ball of mass 200 g travelling at 10ms^(-1)is struck by a hockey sticks so as to return it along its original path with avelocity of 5 ms^(-1) . Calculate the change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick . |
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Answer» Solution :MASS of the hockey ball m=200 g -0.2 kg Hockey ball travels with velocity `v_1=10 m//` Initial momentum `=mv_1` Hockey ball travels in the opposite direction with velocity `v_2=-5m//s` Final momentum `=mv_1 -mv_2` =0.2[10(-50)] `=0.2 (15)=3 kg ms^(-1)` Hence the CHANGE in momentum of the hockey is `3 kg ms^(-1)` |
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| 810. |
The length of the effort arm is greater than that of the load arm in a second-order lever. |
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| 811. |
In each of the following a force, F is acting on an object of mass, m. The direction of displacement is from west to east shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero. |
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Answer» Solution :(a) no displacement (b) force is POSITIVE (WORK is done) (C) work done is negative |
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| 812. |
Which one of the following is most likely not a case of uniform circular motion? |
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Answer» Motion of the EARTH around the Sun |
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| 813. |
What is a stethescope? What is the principle on which it works? |
| Answer» SOLUTION :Stethescope is a medical INSTRUMENT used for LISTENING to sounds produced in the body. In stethescopes, the sounds reach doctor.s ears by multiple reflections that HAPPEN in the CONNECTING tube. | |
| 814. |
Two bodies fall freely from different heights and reach the ground simultaneously. The time of descent for the first body is t_(1) = 2s and for the second t_(2) = 1s. At what height was the first body situated when the other began to fall? (g=10 m//s^(2)) |
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Answer» Solution :The SECOND body takes 1 second to reach ground. So, we need to find the distance traveled by the first body in its first second and in two seconds. The distance covered by first body in 2s, `h_(1)=1//2 GT^(2) =1//2 xx10xx2^(2)=20 m`. The distance covered in `1s, h_(2)=5 m`. The HEIGHT of the first body when the other begin to fall H =20-5 =15 m. |
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| 815. |
An automobile vehicle has a mass of 1500 kg . What must be the force between the vehicle and road if the vehicle is to be stopped with a negative acceleration of 1.7 ms^(-2). |
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Answer» Solution :Mass of the automoblile vehile , m=1500 kg. Final velocity ,v=o (finally the automobile stops). Acceleration of the automobile ,a=`1.7 MS^(-2)` . From Newton.s second law of motion : force = Mass X Acceleration `=1500 (-1.7)=-2550N`. Hence ,the force between the automobile and the road is -2550 N , in the DIRECTION opposite to the motion of the automobile. |
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| 816. |
State principle of floatation |
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| 817. |
What transformation of energy takes place when current is drawn from a cell ? |
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| 818. |
A person performs 420 J of work in 5 minutes. Calculate the power delivered by him. |
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Answer» <P> SOLUTION :Work done by the person, W = 420 JTime taken to complete the work, t = 5 min=5 x 60S = 300s Power delivered, P = W/t =420/300 = 1.4 W |
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| 819. |
Protential near a charge is the measure of its….. To bring a positive charge at that point. |
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Answer» force |
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| 820. |
If the distance (s), covered by an object is directly proportion to the square of time (t). then the object ....... |
| Answer» SOLUTION : with CONSTANT ACCELERATION | |
| 821. |
A car travels a distance 100 m with a constant acceleration and average velocity of 20 m s^(-1) . The final velocity acquired by the car is 25 m s^(-1). Find : (i) the initial velocity and (ii) acceleration of car. |
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| 822. |
Two cylindrical rods of same length have the area of cross section in the ratio 2:1 rods are made up of same material, which of them conduct heat faster ? |
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Answer» Both RODS |
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| 824. |
The time period of a pendulum clock is : |
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Answer» 1s |
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| 825. |
A car travels with a uniform velocity of 25 m s^(-1) for 5 s. The brakes are then applied and the car is uniformly retarded and comes to rest in further 10 s. Find : (i) the distance which the car travels before the brakes are applied, (ii) the retardation,and (iii) the distance travelled by the car after applying the brakes. |
| Answer» SOLUTION :(i) 125 m (II) 2.5 m `s^(-2)` (III) 125 m | |
| 826. |
Why are sound wave called mechanical wave ? |
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| 827. |
In transferring 1.5 C charge through a wire, 9 J of work is needed. Find the potential differenceacross the wire. |
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| 828. |
Why do nails have pointed tips ? |
| Answer» SOLUTION :The force EXERTED when acts on a SMALLER area, it EXERTS LARGER pressure. So the nails have pointed tips. | |
| 829. |
Masses of two bodies are 1kg and 4kg respectively. If their kinetic energies are in 2:1 proportion, ratio of their speeds is …………… |
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Answer» `2sqrt(2):1` Now, `(K_(1))/(K_(2))=((1)/(2)m_(1)v_(1)^(2))/((1)/(2)m_(2)v_(2)^(2))=((1kg)v_(1)^(2))/((4kg)v_(2)^(2))` `THEREFORE (2)/(1)=(1)/(4)(v_(1)^(2))/(v_(2)^(2)) therefore (v_(1)^(2))/(v_(2)^(2))=(8)/(1) therefore (v_(1))/(v_(2))=(2sqrt(2))/(1)` |
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| 830. |
What is the work to be done to increase the velocity of a car from 30kmh^(-1) to 60kmh^(-1), if the mass of the car is 1500kg? |
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Answer» Solution :Mass of the car `m=1500kg`, Initial velocity of car `U=30kmh^(-1)` `=(30xx1000m)/(60xx60s)` `=(25)/(3)ms^(-1)` Similarly, the final velocity of the car, `v=60kmh^(-1)` `=(50)/(3)ms^(-1)` Therefore, the initial kinetic energy of the car, `E_(kl)=(1)/(2)m u^(2)` `=(1)/(2)xx1500kgxx((25)/(3)ms^(-1))^(2)` `=(156250)/(3)J` The final kinetic energy of the car, `E_(kf)=(1)/(2)xx1500kgxx((50)/(3)ms^(-1))^(2)` `=(625000)/(3)J` Thus, the work done = Change in kinetic energy `=E_(kf)-E_(kl)` `=156250J` |
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| 831. |
Hold a concave mirror in your hand (or place it in a stand). Direct Its reflecting surface towards the sun. Direct the light reflected by the mirror onto a sheet of paper held not very far from the mirror. Move the sheet of paper back and forth gradually until you find a bright, sharp spot of light on the paper. Position the mirror and the paper at the same location for few moments. What do you observe? Why does the paper catches fire? |
| Answer» Solution :The concave mirror FOCUS the sunlight at one particular point. At that particular point, amount of sunlight is CONVERGED and heat is TRAPPED at that point. This is because, it BURN the paper on which the image is focused. | |
| 833. |
If the orbital velocity of the moon is 1020 m s^(-1), find the time taken by the moon to complete one revolution around the Earth. Explain why this period is different from the period that is observed from the Earth, which is 29.5 days. (Take the distance of the moon from the Earth as 3.4 xx 10^(8) m, "and" (1)/(86400) = 1.157 xx 10^(-5)) |
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Answer» Solution :(i) Here the force of attraction between the moon and the Earth can be obtained by using the formula `F = (GM_(e)m_(m))/(r^(2)) = (m_(m)V^(2))/(r)` Find the VALUE of v and r from given data But,`""v = (2 pi r)/(T)` Obtain the value of 'T'. Since 1 day has 86400 s. Find the NUMBER of DAYS the moon takes for one revolution around the Earth as observed from earth. Divide 'T' by 86400 s to get the value of 'T' in terms of the number of days. What is a sidereal month and a synodic month? (ii) 29.5 days |
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| 834. |
How does an object's density determine whether the object will sink or float in water? |
| Answer» SOLUTION :Whether an OBJECT will sink or float in ALIQUID is determined by the density of the object compared to the density of the LIQUID. If the density of a substance is less than the density of the liquid it will float. For EXAMPLE, a piece of wood which is less dense than water will float on it. Any substance having more density than water (for example, a stone), will sink into water. | |
| 835. |
Two metallic tins made of copper and steel are stuck together with the copper tin inside the steel tin. Explain a method to seprate the tins. |
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Answer» SOLUTION :Which among copper and STEEL has greater coefficient of expansion ? GIVEN that the copper VESSEL is stuck inside the steel vessel, which of HEATING or cooling the vessels, creates a space between them to get detached ? |
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| 836. |
The main scale reading while measuring the thickness of a rubber ball using Vernier Caliper is 7 cm and the Vernier scale coincidencs is 6 . Find the radius of the ball . |
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Answer» SOLUTION :GIVEN :The main scale reading = 7 cm VERNIER scale coincidence = 6 We know that least count of vernier= 0.01 cm The radius of the ball= MSR + VC `xx` LC = 7 cm + 6 `xx` 0.01 cm = 7 cm + 0.06 cm = 7 . 06 cm |
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| 837. |
A car acquires a velocity of 72 km h^(-1) In 10 s starting from rest. Calculate : (i) the acceleration, (ii) the average velocity, and (iii) the distance travelled in this time. |
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Answer» Solution :Given INITIAL velocity U =0 Final velocity v= 72 KM `h^(-1)` `= (72xx1000 m)/(60xx60s)= 20 m s^(-1)` TIME taken t = 10 s (i) Acceleration a = `(v-u)/(t)` `=((20-0)m s^(-1))/(10 s)= 2 m s^(-2)` (ii) Average velocity = `= (0 +20)/(2) m s^(-1) = 10 m s^(-1)` (iii) Distance travelled S = average velocity `xx` time `= (10 m s^(-1)) xx (10 s)` = 100 m Alternative method : Distance travelled S = `ut+ (1)/(2) at^(2)` = `0 +(1)/(2) xx2 xx(10)^(2)= 100` m |
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| 838. |
A body starts with an initial velocity of 10 ms and acceleration 5 ms. Find the distance covered by it in 5 s. |
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| 839. |
It is necessary to wind the clock regularly to run it. |
| Answer» SOLUTION :Because the wound spring possesses (elastic) potential energy due to its CONFIGURATION. When spring UNWINDS, its potential energy is converted into kinetic energy which makes the hands of clock ROTATE. When spring totally unwinds, the potential energy becomes ZERO. To keep the clock going on, one has to wind the spring again. | |
| 840. |
Ocean waves of time period 10 s have wave velocity 15 ms^(-1). Find the wavelength of these waves . |
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Answer» SOLUTION :GIVEN , T= 10 s, V= 15 m `s^(-1)` From relation `V= lambda/T` Wavelength of wave`lambda = V XX T` or ` lambda = 15 xx 10 = 150 m` |
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| 841. |
A balance similar to a Roman steel yard is constructed suchthat the length of the scale on the beam of the balance is 50 cm and the least count on thescale is 1 mm. The zero mark of the scale is at a distance of 15 cmfrom the point of suspension of thebalance. The hook that isused to attach the loads and the centre of gravity of thebeam are at distance 8 cm and 5 cm, respectively,from its fulcrum. If the weight of the rider of the balance is 50 gf, find the weight of thebeam, the maximum load that can be measured using the balance and its least count. |
Answer» Solution :The information given in the question can be depicted as shown in the figure.  G is the POSITION of centre ofgravity. H is theposition of the hook, O is the fulcrum, A and B are zero cm mark and 50 cm mark of the scale on the beam Given OG=5 cm, OH = 8 cm andOA = 15 cm Mass of the rider R = 50 gf. Let x g be themass of the beam Then x (OG) = R(OA) `X=(R(OA))/(OG)=(50xx15)/(5)=150g` THUS, the weight of thebeamis 150 gf Let L be the maximum load that is attached to the balance. Then `L(OH)+ x(OG)=R(OB)` `L=(R(OB)-x(OG))/(OH)=(50(65)-150(5))/(8)` `=312.5 g` The distance moved by the rider on the scale from its zero mark is directlyproportional to the load attached. Thus, 50 cm (=500 mm) corresponds to 312.5 g. Thus, the least count of the balance = 0.625 g |
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| 842. |
The speed of light in air is : |
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Answer» `3XX10^8 m s^(-1)` |
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| 843. |
What would have happened if nature had not allowed the transformation of energy ? |
| Answer» SOLUTION :Life would not have been possible. To run life, we need energy in its VARIOUS forms to enable us to walk, talk, HEAR, think, to travel to DIFFERENT places and so on. | |
| 844. |
Find out the odd one....(a)Hydraulic press(b)Hydrometer(c)Hydraulic jack(d)Excavator |
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Answer» HYDRAULIC press |
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| 845. |
The conversion of part of energy into an unuseful form of energy is called…………… |
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| 846. |
A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force. Let us take it that the force acts on the object through the displacement. What is the work done in this case? |
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Answer» `W=Fxxs` `=7Nxx8m=56Nm=56J` |
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| 847. |
A piece of wood of uniform cross section and height 15 cm floats vertically with its height 10 cm in water and 12 cm in spirit. Find the density of (i) wood and (ii) spirit |
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| 848. |
{:((1),"Force between the sum & moon",(a),F=Gm_(1)m_(2)ld^(2)"sum and moon"),((2),"Gravitational constant G",(b),"used to determine acceleration due to gravity"),((3),"Simple pendulum",(c),"depends on masses"),((4),"Newton's law of gravitation",(d),"Action at a distance"),(,,(e),"is universal"):} |
| Answer» Solution :`1-(d),2,(E),3-(b),4-(a)` | |
| 849. |
Two hydrogen gas balloons having the same pressure and whose volumes are in the ratio of 1:2, resoectively, are relased simultaneously into air on the surface of the Earth. Find the ratio of time taken to reach a height of 100 m from the ground. (Neglect the air friction) |
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Answer» Solution :`1:1` `F_("Net")=U-W` `V_(b)d_(b)a_("Nrt")=V_(b)*d_("air")*g-V_(b)*d_(b)*g` `a_("Net")=(g(d_("air")-d_(b)))/(d_(b))` `a_("Net")` is independent of volume of the BODY. Here the two BALLOONS have same pressure, so their DENSITIES will also be equal. Therefore, they take same time to reach the given height. |
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| 850. |
While fixing a nail in a wooden block, the hammer is raise and brought on it. |
| Answer» SOLUTION :Because when a raised hammer is brought on the NAIL speedily, its velocity increases and hammer gains more kinetic ENERGY. More WORK can be obtained due to more kinetic energy of the hammer. So, nail can be fixed easily in the wooden BLOCK. | |