The radium isotope 223Ra, an alpha emitter, has a half-life of 11.43 days. You happen to have a 1.0 g cube of 223Ra, so you decide to use it to boil water for tea. You fill a well-insulated container with 460 mL of water at 16∘ and drop in the cube of radium.

5g of ammonium nitrate was dissolved in 60g of water in an insulated container. the temperature at the start of the reaction was 23.0°c and at the end it was 19.0°c. calculate the energy absorbed by the reaction.

If a star is moving toward earth, it is

Aballoon is rising vertically upwards at a velocity of 10m/s. when it is at a height of 45m from the ground, a parachute bails out from it. after 3s he opens his parachute and decelerates ata a constant rate 5m/s.when. (a) what was the height of the parachutist above the ground when he opened his parachute? (b)how far is the parachutist from the balloon at t=3s? (c)with what velocity does the parachutist hit the ground? (d)after how long does the parachutist hit the ground after his exist from the balloon?