Half life of `.^35S` is87.8 D.What percentage of `.^35S` sample remians after 180 d?

Half life .^87Ga is 78 h.How long will it take to decay 21% of sample of Ga?

Half life of radon is 3.82 d.By what itme would 99.9% of radon will be decayed.

A black body of mass 32g, specific heat = 0.1 cal^@c and area 8 cm^2 at a temperature of 300^C is kept in an enclosure maintained at 0^C . If the body cools at the rate of 0.35 ^@C//s , calculate Stefan’s constant. J = 4.18 joule/cal.

The acceleration due to gravity on the surface of moon is 1.7 ms ^-2 . What is the time period of a simple pendulum on the surface of moon if its time period of the surface of earth is 3.5 s ? (g on the surface of the earth is 9.8 ms^-2