Question1
A theory of nuclear astrophysics proposes that all the elements heavier than iron are formed in supernova explosions ending the lives of massive stars. Imagine equal amounts of 235U and 238U were created at the time of the explosion and the present 235U/238U ratio on the Earth is 0.007 25. The half-lives of 235U and 238U are 7.04 108 yr and 4.47 109 yr, respectively. How long ago did the star(s) explode that released the elements formed the Earth?
Question2
A circular conducting loop with a radius of 0.35 m and a small gap filled with a 10.5 Ω resistor is oriented in the xy-plane. If a magnetic field of 1.5 T, making an angle of 30° with the z-axis, increases to 15.0 T, in 7.0 s, what is magnitude of the current that will be caused to flow in the conductor?
Question3
Marianne really likes coffee, except on summer days she doesn't want to drink a hot beverage. If she is served 240ml of coffee at 88C in a well-insulated container, how much ice at 0C should she add to get a final temperature of 34C?