Question

Q1.Very shorrt answer type questions : (2×5=10)

(a) (i)1eV =___________ J

(ii)1kWh=_________J

(b) What is the work done by coolie carrying a load going:

(i)upstairs

(ii)downstairs

(c ) If two bodies A having mass ‘m’and body B has mass ‘M’ so that m<M , both posses same kinetic

energy which has more momentum and why ?

(d)What is degraded energy? Explain with an example.

(e) An electric heater of power 3kW is used for 10h. How much energy does it consumed in kWh and in

joule.

Q2.Short answer questions: (3×5=15)

(a)Give the energy conversions in the following:

(i)nuclear power plant (ii) charging battery (iii)cracker explosion

(b)Discuss the law of conservation of energy of freely falling body with suitable diagram.

(c) A ball of mass 10g falls from a height of 5m .It rebounds from the ground to a height of 4 m .Find:

(i)initial potential energy of ball

(ii) the kinetic energy of ball just before striking the ground

(iii) the kinetic energy of ball just after striking the ground.

(d)Complete the following;

(i) When the mechanical energy changes to other forms , it is always in the form of _________ energy.

(ii)the physical quantity which is measured in calorie is_______

(ii)the physical quantity which is measured in H.P is_______

(e ) A boy takes 3 minutes to lift a 20 litre of water bucket from a 20 m deep well, while his father does

it in 2 minutes .

(i) Compare their work and power developed by them.

(ii) How much work each does? Take density of water 1000kg/m^3 and g=9.8m/s^2​

Answer 1

Answer:

Consider the following,

work done is written as W = F.s = FsCosθ here F is the force applied, s is the displacement caused such that

F = mg = 10 X 10 = 100 N s

W( horizontal direction)= FsCos(0)=500J , θ is the angle between (vectors) F and s now,

as F and s are perpendicular for vertical direction, θ = 90 thus, W = FsCos90 = 0