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Physics numericals

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Physics numericals

1. 1. Q. a cube of mass 1kg with each side of 1cm is lying on the table. find thepressure exerted by the block onthe table. take g=10 m/s2Ans: Pressure is given as force/area so, Force, F = mg = 1000 X 981 gm.m/s2and area, A = 1x1 cm2 = 1cm2Thus, the pressure exerted would be P = (981 X 1000) / 1 orP = 9.81 X 10 5 paQ. The mass of a solid iron cube of side 3cm is to be determined usig a spring balance. If the of iron isapproximately 8.5 g/cm3, the best suited spring balance for determining weight of the solid would be of1. range 0-250gwt ; least count 1gwt2. range 0-250gwt ; least count 5gwt3. range 0-1000gwt ; least count 5gwt4. range 0-1000gwt ; least count 10gwtAns: Edge=3 cm , Density=8.5 g/cm3Mass= density x volume = 8.5 x(3x3)=229.5gwt. Therefore secondspring balance of range 0-250 gwt with least count 5gwt will be suitable.Q. The density of turpentine oil is 840 Kg/ m3. What will be its relativedensity. (Density of water at 4degree C is 10 cube kg minus cube)Ans:Relative Density = Density of Substance/ Density of water at 4 0cDensity of turpentine oil = 840 kg/m3 ( given).Density of water at 4 0c = 1000 kg/ m3Relative density of turpentine oil = Density ofturpentine oil / Density of water at 4 0c= (840 / 1000 ) kg m-3/ kg m-3 = 0.84Since, the relative density ofthe turpentine oil is less than 1, therefore it will float in water.Q. A solid body of mass 150 g and volume 250cm3 is put in water . will following substance float or sinkif the density of water is 1 gm-3?Ans:Q. a cube of mass 1kg with each side of 1cm is lying on the table. find the pressure exerted by the blockon the table. take g=10 m/s2Ans: Pressure is given as force/area so, Force, F = mg = 1000 X 981 gm.m/s2and area, A = 1x1 cm2 = 1 cm2Thus, the pressure exerted would be P = (981 X 1000) / 1 or P = 9.81 X 10 5 paQ. The mass of a solid iron cube of side 3cm is to be determined usig a spring balance. If the of iron isapproximately 8.5 g/cm3, the best suited spring balance for determining weight of the solid would be of1. range 0-250gwt ; least count 1gwt 2. range 0-250gwt ; least count 5gwt3. range 0-1000gwt ; least count 5gwt 4. range 0-1000gwt ; least count 10gwtAns: Edge=3 cm , Density=8.5 g/cm3Mass= density x volume = 8.5 x(3x3)=229.5gwtTherefore second spring balance of range 0-250 gwt with least count 5gwt will be suitable.
2. 2. Q. The density of turpentine oil is 840 Kg/ m3. What will be its relative density. (Density of water at 4degree C is 10 cube kg minus cube)Ans:Relative Density = Density of Substance/ Density of water at 4 0cDensity of turpentine oil = 840 kg/ m3 ( given).Density of water at 4 0c = 1000 kg/ m3Relative density of turpentine oil = Density of turpentine oil / Density of water at 4 0c= (840 / 1000 ) kg m-3/ kg m-3 = 0.84Since, the relative density of the turpentine oil is less than 1, therefore it will float in water.Q. A solid body of mass 150 g and volume 250cm3 is put in water . will following substance float or sinkif the density of water is 1 gm-3?Ans: The substance will float if its density is less than water and will sink if its greater.so, density of solid body is d = mass/volumeor d = 150/250 = 0.6 gm/cm3 which is less than the density of water (1 gm/3).So, the solid body will float on water.Q. A body weighs 50 N in air and when immersed in water it weighs only 40 N. Find itsrelative density.Ans: the relative density would be ratio of the density of the body with respect to air and the density ofthe body with respect to water.so, F1 = 50 N F2 = 40 Nso, F1/F2 = 50/40 or relative masses m1/m2 = 5/4 anddensity = mass/volume and as volume remains constant,Relative density = d1/d2 = 5/4Q. A ball of relative density 0.8 falls into water from a height of 2m. find the depth to which the ball willsink ?Ans: Speed of the ballV = 2gh =  2x10x2 = 6.32 m/sBuoyancy force by water try to stop the ball.Buoyancy force = weight of displaced water = dx Vxgwhere d = density of water V = volume of the ball , g = 10 m/s2deceleration of the body by buoyancy force, a = (dVg)/ mwhere m= dV d = density of blocka = dVg/(d V) = dg/d =(d/d)*g =g/(0.8)= 10/0.8 (Given, d/d = 0.8)= 12.5 m/s2Net deceleration of ball,a = a-g = 2.5 m/s2Final speed of ball v = 0 Use v 2 = v2 + 2as s= depth of ball in the water=> 40 = 0 + 2x2.5xs => s = 8m
3. 3. Q. Equal masses of water and a liquid of relative density 2 are mixed together. Then, the mixture hasa relative density of (in g/cm3) a)2/3 b)4/3 c)3/2 d)3Ans: he masses of two liquids are equal, let it be m.Let the relative densities of water and liquid be ρ1 and ρ2 respectively.The volume of the two be V1 and V2, of water and liquid respectively.The volume of the mixture would be, V = V1 + V2 (1)also, volume = mass/densitythus,2m/ρ (V) = m/ρ1 (V 1 ) + m/ρ2 (V 2 )here ρ1 = 1,ρ2 = 2 and ρ is the relative density of the mixture.now,2/ρ = 1/ρ1 + 1/ρ2by substituting the values, weρ/2 = 2/3or, the relative density of the combined liquid will be, ρ=4/3 Density Problems1) What is the volume of a tank that can hold 18 754 Kg of methanol whose density is 0.788g/cm3?2) What is the density of a board whose dimensions are 5.54 cm x 10.6 cm X 199 cm and whose mass is 28.6 Kg?3) CaCl2 is used as a de-icer on roads in the winter. It has a density of 2.50 g/cm3. What is the mass of 15.0 L this substance?4) In the Macys Thanksgiving day parade, 2000, there was a new float, the Cheerios bee, Buzzbee. The jar of honey it was holding contained 36,763 L of helium. The honey jar was 1/10 of the body size. What is the volume of the entire float? If the density of helium is 0.000178 g/cm3, what is the mass of the helium for the entire float in Kg?5) My gas tank in my car has a total volume of 68 L. The manual says the gas gauge light will come on when there are only 5 L remaining in the tank and that the car will not be able to draw on the last 2 L in the tank. Practically speaking, what is the functional volume of the gas tank? If I ran out of gas, the car wont go, and I put in 5 L of gas, what is the total volume of gas in my tank? If 5 L of gas has a mass of 450 Kg, what is the mass of the gas in my tank?