Question

26.) A mass of 5kg is on top of a building of height 10m. Calculate its potential energy. The mass then falls at a speed of 8 m/s in 4 sec, find its KE and momentum p. What is the Force and impulse the mass transfers to the ground? 27.) For problem 26 above, find the work done by gravity if the mass falls a distance 2 meters. If the mass falls for 11 seconds, what is the energy expended by this force? 28.) Two charged pellets, each with a charge of 5C, are located a distance 15m apart. What is the electric force between the two pellets? 29.) What is the resistance of a toaster that draws a current of 12A when connected to a 120V circuit? 30.) What is the speed of an EM wave that has a frequency of 10000 Hz and a wavelength of 0.005m?

Answer 1

The potential energy work and force

1 Potential energy Pe= mgh PE= 3 x 9.8 x 10 IP6= 4 90 I Kinetic energey Ke= £mre Kez 4XS (8)2 = 11601 Momentum P = mv=5x8= 4omic at grand v=528ł V = V2x9.8x10. v= 14 mis then impulse - AP= (o-14) XS - 151= 70 kg mis

wok done by gravity w = mgh sxg.& x2 I8 I Z n = 10 = Į at? £ a ( 113² a=20 121 then force f = ma loo 121 then energy expended is- E = f. h = 1000 121 -18.26 I (28) The electric force is given as

f = K9192 - 72 f = 9x109 x sxs = (15) 2 If = 109 w According to ohm's Law - v=IR 2 R = X R = 120 = 1102 29 12 Speed v= fx v = 10000 x odos ? v= somis