(i)A manis standing between two vertical wall 680 m apart. He claps his hands and hears two distinct echoes after 0.9 secondsand 1.1 seconds respectively .What is the speed of sound in the air ? (ii) An electric heater of resistance 5Omega is connected to an electric source .If a current of 6 A flows through the heater then find the amount of heat produced in 5 minutes.

(i)A manis standing between two vertical wall 680 m apart. He claps hi

1.	(i)A manis standing between two vertical wall 680 m apart. He claps his hands and hears two distinct echoes after 0.9 secondsand 1.1 seconds respectively .What is the speed of sound in the air ? (ii) An electric heater of resistance 5Omega is connected to an electric source .If a current of 6 A flows through the heater then find the amount of heat produced in 5 minutes.
Answer» Solution :`Velocity =("Distance travelled by sound")/("Time taken")` `v=(2d)/(t)` `d_1=(vt_1)/(2)& d_2=(vt_2)/(2)` `d_2=(v)/(2)(t_1+t_2)` `v=(2d)/((t_1+t_2))` `=(2xx680)/((0.9+1.1))``v=680ms^(-1)` (ii) GIVEN resistance R=5 `Omega`,current I=6A Time t=5 minutes =`5xx60s` =300s AMOUNT of HEAT produced, H=`I^(2)Rt` `H=6^(2)xx5xx300`. Hence H=5400J