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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.
| 1. |
The force required just to move a body up an inclined plane is double the force required just to prevent the body sliding down. If the coefficient of friction is `0.25` , the angle of inclination of the plane isA. `36.8^(@)`B. `45^(@)`C. `30^(@)`D. `42.6^(@)` |
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Answer» Correct Answer - A |
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| 2. |
What is static friction? |
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Answer» Static friction is the friction which comes into play when surfaces of objects are at rest relative to each other |
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| 3. |
Adjacent experiment representsA) Understanding the nature of friction and the concept of static frictionB) Observing variation of friction C) Effect of area of contact of frictional area D) None of the above |
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Answer» A) Understanding the nature of friction and the concept of static friction |
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| 4. |
Write any one precaution which was taken by you while doing the experiment to understand the nature of friction. |
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Answer» Keep the weights to the hanger slowly and one by one. |
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| 5. |
A block of 1 kg is stopped against a wall by applying a force F perpendicular to the wall. If `mu=0.2` then minimum value of F will beA. 980 NB. 49 NC. 98 ND. 490 N |
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Answer» Correct Answer - B |
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| 6. |
A block weighs W is held against a vertical wall by applying a horizontal force F. The minimum value of F needed to hold the block isA. Less than WB. Equal to WC. Greater than WD. Data is insufficent |
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Answer» Correct Answer - C |
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| 7. |
The length of a simple pendulum of 0.4 m. The bob of the pendulum is drawn aside till the string is horizontal, it is then released from this horizontal position, What will be its velocity when it reached the lowest point in its swing ? `(g = 9.8 m//s^(2))` [Hint : Loss in potential energy = gain in kinetic energy] |
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Answer» Correct Answer - `2.8 ms^(-1)` |
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| 8. |
If the system if Figure 7.13 is released from rest in the configuration shown by solid lines, find the maximum distance `h` through which the weight will fall. (Neglect friction and masses of pulleys) What will happen if `P = 2Q` ? [Hint : Apply work-energy theorem to the compound system consisting of the three masses and ceiling. To find intantaneous velocities of the masses apply the condition that the length of the string remains constant. Also remember that gravitational pulls are the lone forces external to the system, the tension of the string and pull the internal force ceiling are of the system] |
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Answer» Correct Answer - `h=4PQl//(4Q^(2)-P^(2))`. The system will acquire terminal velocity `= sqrt(gl)` |
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| 9. |
A body moves in a straight line under the action of a variable force which changes with displacement of the body as shown in the figure. What is the work done when the body has been displaced through (i) 0.2 m, (ii) 0.4 m ? |
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Answer» Correct Answer - 0.2 J |
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| 10. |
Two masses 1.65 kg and 3.30 kg are joined together by a massles rod parallel to an incline to `30^(@)`, over which both slide down, with the 1.65-kg mass trailing behind the 3.30-kg mass. The coefficient of friction between the first mass and the plane is 0.226 and that between the second mass and the plane is 0.113 Find (a) the tension in the rod, (b) the common acceleration of the two masses [Hint : Make free-body diagram of the two bodies and consider their motion along and perpendicular to the plane] |
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Answer» Correct Answer - `1.06 N,3.6 ms^(-2)` |
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| 11. |
What work should a man do to walk up a subway escalator moving down with speed `v` ? The height of the escalator is `h`, and the man walks up the escalator at a speed u. |
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Answer» Correct Answer - `mgh(1+(v)/(u+v))` |
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| 12. |
What power is developed by a grinding machine whose wheel has a radius of 20 cm and runs at 2.5 revolutions per second when the tool to be sharpened is held against the wheel with a force of 20 kg ? The coefficient of friction between the tool and the wheel is 0.3 [Hint : Power `= Fv = F omega r = mu N omega r` where N is the normal reaction] |
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Answer» Correct Answer - 184.7 W |
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| 13. |
Calculate of velocity `v` of the falling masss P after it has gone down by `x` in an axle and wheel system of radii r and R respectively (Figure 2.12) [Hint : Let Q go up by `y` when P down by x Then `(x)/(y)=(R)/(r) :. x=(R)/(r)y` Apply work-energy theorem to the system (P+Q+ceiling). Remember that the gravitational pulls are the lone forces external to the system, the tensions and pull of ceiling are internal forces of the system] |
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Answer» Correct Answer - `sqrt(2gx(P-(r)/(R)Q)//(P+(r^(2))/(R^(2))Q))` |
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| 14. |
A flexible but inextensible chain of length `l` is placed on a smooth table with an initial length `1 = nl` hanging down the table. Calcultae the velocity with which the chain will leave the table if released from rest. Consider two cases : (i) the hanging part does not touch the ground which is at a large distance, (ii) the lower end of the hanging part initially just touches the ground. Also calculate the time in which the chain leaves the table in the first case [Hint : Taking the table as the datum and `m` as the mass per unit length of the chain, apply the principle of conservation of energy]. |
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Answer» Correct Answer - (i) `v=sqrt(gl(1-n^(2)))t,=sqrt((l)/(g)ln)((1+sqrt(1-n^(2)))/(n))` (ii) `v=sqrt(2nlg l n(1)/(n))` |
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| 15. |
Assuming that a car whose CG is at a height `b` from the rear wheel and at a distance c from the front wheel and at a height `h` above the pavement, has sufficient power and there is sufficient friction, find the maximum acceleration that it would be able to develop without tipping over backward. |
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Answer» Correct Answer - `(bg)/(h)` |
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| 16. |
A car starts moving from rest along the circumference of a horizontal circle of radius `R =49` m with a constant tangential acceleration `a_(t)=0.62 ms^(-2)`. The coefficient of sliding friction is `mu = 0.2`. What distancem will the car describe without sliding ? [Hint : The car will start sliding when the frictional force attains its upper bound] |
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Answer» Correct Answer - `s=(1)/(2)Rsqrt((mug//a_(t))^(2)-1)=60m` |
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| 17. |
State the reason for sprinkling of fine powders on the carrom board. |
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Answer» Power is sprinkled on the carrom board because the powder fills the cuts in the wood of the board and hence reduces the irregularity and hence the friction reduces, so the powder is used to reduce the friction on the carrom board. |
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| 18. |
Which of the following should be used to reduce friction on a carrom board? A. a lubricating oil B. a dry lubricant C. a layer of grease D. a ball bearing |
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Answer» B. a dry lubricant Using talcum powder to reduce the friction on carom board. |
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| 19. |
Why do we sprinkle fine powder on carrom board? |
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Answer» Sprinkling fine powder on carrom board reduces friction between carom and striker. |
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| 20. |
Can you accelerate a car on a friction-less horizontal road by putting more petrol in the engine? Can you stop a car going on friction-less horizontal road by applying brakes? |
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Answer» A car can not be accelerated by putting more petrol in the engine on a friction-less horizontal road because force of friction would not develop which is necessary for acceleration. Same is the case of stopping the car on such surface. Due to lack of the friction no retarding force would develop. |
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| 21. |
Why is it difficult to walk on a smooth floor? |
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Answer» It is difficult to move on a smooth floor because when we push the floor back there is no frictional force to stop our foot from going back and our foot keeps on going back by slipping on the surface and hence we do not get any reaction force from the ground to move forward, so it is difficult to walk on a smooth floor. |
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| 22. |
Why does a fast car slow down if its engine is switched off? |
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Answer» When the engine of a car is switched off, then there is no energy available for the engine to oppose the frictional forces. Thus, the engine slows down and eventually comes to rest. |
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| 23. |
We always apply powder to a carom board. Why? |
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Answer» We apply powder to carom board because the wood has a frictional surface and to reduce the friction powder is sprinkled on the board as the powder fills the gaps on board, so the striker moves smoothly and at large distance with even lower force. |
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| 24. |
Fill in the blanks (a) Friction opposes the ________between the surfaces in contact with each other. (b) Friction depends on the _________of surfaces. (c) Friction produces _________. (d) Sprinkling of powder on the carrom board ________friction. (e) Sliding friction is ________than the static friction. |
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Answer» (a) Friction opposes the motion between the surfaces in contact with each other. (b) Friction depends on the nature of surfaces. (c) Friction produces heat. (d) Sprinkling of powder on the carrom board reduces friction. (e) Sliding friction is less than the static friction. |
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| 25. |
A boat or an aeroplane has a pointed or tapering front / head. Why? a) To increase the friction of fluid b) To reduce the friction of fluid c) To look good d) For no reason |
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Answer» b) To reduce the friction of fluid |
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| 26. |
Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangements are given below. Choose the correct arrangement. (a) rolling, static, sliding (b) rolling, sliding, static (c) static, sliding, rolling (d) sliding, static, rolling |
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Answer» (c) static, sliding, rolling |
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| 27. |
Name the force which always opposes motion. |
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Answer» Frictional force always opposes the relative motion between two surfaces and always acts opposite to the direction of motion. |
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| 28. |
The unit of force is A) metre B) km C) kilogram-weightD) joule |
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Answer» C) kilogram-weight |
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| 29. |
Four children were asked to arrange forces due to rolling, static and sliding frictions in an increasing order. Their arrangements are given below. Choose the correct arrangement. a) Rolling, Static, Sliding b) Static, Rolling, Sliding c) Rolling, sliding, static d) Sliding, Static, Rolling |
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Answer» c) Rolling, sliding, static |
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| 30. |
The frictional force exerted by fluids is called A) rolling friction B) sliding friction C) drag D) normal force |
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Answer» Correct option is C) drag |
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| 31. |
The frictional force exerted by fluids is also called .........a) drug b) drag c) drop d) drown |
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Answer» The frictional force exerted by fluids is also called drag. |
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| 32. |
The frictional force exerted by a fluid is called: A. brag B. drab C. drag D. tread |
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Answer» C. drag The frictional force exerted by fluids is called drag force. |
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| 33. |
What is the special name of frictional force exerted by fluids (like air or water)? |
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Answer» Drag is the special name of frictional force exerted by fluids. |
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| 34. |
Consider the situation shown in figure (6-Q1). The wall is smooth but the surfaces of A and B in contact are rough. The friction on B due to A in equilibrium(a) is upward (b) is downward (c) is zero (d) the system cannot remain in equilibrium. |
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Answer» (d) the system cannot remain in equilibrium. Explanation: Since the wall is smooth, there is no force to counter the weight of the blocks i.e. sum of forces in vertical direction is not zero, Hence the system cannot remain in equilibrium. |
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| 35. |
Name the force which increases when the two surfaces in contact are made more rough. |
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Answer» Frictional force increases when the two surfaces in contact are made more rough. |
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| 36. |
In a situation the contact force by a rough horizontal surface on a body placed on it has constant magnitude. If the angle between this force and the vertical is decreased, the frictional force between the surface and the body willA. increaseB. decreaserC. remain the sameD. may increse or decrease |
| Answer» Correct Answer - B | |
| 37. |
Consider the situation shown in figure (6-Q1). The wall is smooth but the surfaces of A and B in contact are rough. The friction on B due to A in equilibrium(a) is upward (b) is downward (c) is zero(d) the system cannot remain in equilibrium. |
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Answer» (d) the system cannot remain in equilibrium. Explanation: Since the wall is smooth, there is no force to counter the weight of the blocks i.e. sum of forces in vertical direction is not zero, Hence the system cannot remain in equilibrium. |
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| 38. |
Consider the situation as shown in the figure. The maximum value of `m` so that the blocks do not move is A. `0.2 kg`B. `0.4 kg`C. `0.6 kg`D. `0.8 kg` |
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Answer» Correct Answer - B `mg le mu_(s) (2g) rArr m le ( 2 mu_(s) = 2 xx 0.2)` `m le 0.4 kg` |
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| 39. |
Two small blcok `m=2kg` each kept on wedge of mass `12 kg`. There is no friction between blocks and wedge coefficient of friction between wedge and ground in `mu=0.3`. Calculate frictional force by ground on wedge. |
| Answer» `f= mg sin 60 cos 60-mg sin 30 cos 30 f=0` | |
| 40. |
In the shown figure, four blocks `A, B ,C` and `D` are connected by three ideal strings. Coefficient of friction between `A,B` and surface is `0.2`. The mass `A, B` and `D` are of `5 kg` and `C` is of `m kg.f_(A)` and `f_(B)` are the frictional forces action on `A` and `B` respectively. The system is allowed to move. Based on the above data answer the following questions. ( Take `g=10m//s^(2)`) If `m=5 kg`, thenA. `T_(2)=50N, f_(A)=f_(B)=10N`B. `T_(2)=40N,f_(A)=f_(B)=10N`C. `T_(2)=50 N, f_(A)=f_(B)=0`D. `T_(2)=40N, f_(A)=f_(B)=0` |
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Answer» Correct Answer - C Since in absence of friction no motion will occur. So no friction force will act on any mass. |
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| 41. |
Assertion: Two bodies of masses `M` and `m(M gt m)` are allowed to fall from the same height if the air resistance for each be the same then both the bodies will reach the earth simultaneously. Reason: For same air resistance, acceleration of both the bodies will be same.A. If both assertion and reason are true and t he reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explanation of the assertion.C. If assertion is true but reason is falseD. If the assertion and reason both are false |
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Answer» Correct Answer - D |
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| 42. |
Which of the following friction has self adjusting force? A) Sliding friction B) Static friction C) Rolling friction D) Fluid friction |
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Answer» B) Static friction |
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| 43. |
Assertion: Friction is a self-adjusting force. Reason: Friction does not depend upon mass of the bodyA. If both assertion and reason are true and t he reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explanation of the assertion.C. If assertion is true but reason is falseD. If the assertion and reason both are false |
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Answer» Correct Answer - D |
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| 44. |
In the adjacent figure, x-axis has been taken down the inclined plane. The coefficient of friction varies with `x` as `mu=kx`, where `k= tan theta`. A block is released at `O` Maximum distance traveled by block:A. `1 m`B. `2 m`C. `3 m`D. `(1)/(2)m` |
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Answer» Correct Answer - B For `u = 0, x = 0, x = 2m` |
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| 45. |
What is the maximum value of the force F such that the block shown in the arrangement, does not move? A. 20 NB. 10 NC. 12 ND. 15 N |
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Answer» Correct Answer - A |
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| 46. |
Which is easier to hold in hand: a kulhar (earthen pot) or a glass tumbler? Why? |
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Answer» It is easier to hold a kulhar (an earthen pot) because it more rough surface as it is made from mud. Mud offers more friction than glass and we are able to from a grip on the earthen plot. |
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| 47. |
A 500 kg horse pulls a cart of mass 1500 kg along a level road with an acceleration of `1ms^(-2)`. ms . If the coefficient of sliding friction is 0.2, then the force exerted by the horse in forward direction isA. 3000 NB. 4000 NC. 5000 ND. 6000 N |
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Answer» Correct Answer - D |
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| 48. |
“Reducing friction to the lowest possible level in machine tools solves the problem of energy crisis and conserve biodiversity”. How do you support the statement? Explain. |
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Answer» Yes, it will solve the problem of energy crisis and conserve biodiversity the reason is the majority of energy wasted in the form of heat energy due to friction. In order to develop more electrical energy we are depending on coal, petroleum, gas, nuclear energy and hydro electricity. The production of energy from these sources except hydroelectric power causing severe air pollution which are affecting animals and plants. So energy should be conserved by means of reducing friction. |
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| 49. |
Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it. |
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Answer» Frictional force is acting opposite to the movement of the book i.e. upwards |
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| 50. |
You spill a bucket of soapy water on a marble floor accidentally. Would it make it easier or more difficult for you to walk on the floor? Why? |
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Answer» It would make it more difficult for us to walk on a soapy floor because layer of soap makes floor smooth. The coating of soapy water reduces the friction and the foot cannot make a proper grip on the floor and it starts getting to slip on the floor. |
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