Use the Hertzsprung-Russell diagram to determine which condition describes each star. Use the arrows to help locate the stars. 1. Betelgeuse
2. the Sun
3. Sirius B

A. The star can no longer support nuclear fusion because it has exhausted its supply of hydrogen.
B. The star’s hydrogen supply is running low, so it is fusing hydrogen from outside the core.
C. The star is experiencing nuclear fusion at its core.

Sobre transformações cíclicas, são feitas algumas afirmações, determine quais estão corretas. i – a variação de energia interna em uma transformação cíclica é nula; ii – o trabalho, em uma transformação cíclica, é sempre positivo; iii – ao completar um ciclo, o gás tem a mesma temperatura com a qual começou a transformação; iv – uma transformação cíclica é, obrigatoriamente, composta de transformações conhecidas, como adiabática, isocórica, etc: a) i e iii b) i e ii c) ii e iii d) i e iv e) iii e iv

3. a lunar exploration vehicle was created by a research team. it weighs 3,000 kg on the earth. it needs an acceleration of 10 m/s2 on the moon. in order to have the same acceleration, what will be the net force acting on the vehicle on the earth?

A980-kg sports car collides into the rear end of a 2300-kg suv stopped at a red light. the bumpers lock, the brakes are locked, and the two cars skid forward 2.6m before stopping. the police officer, estimating the coefficient of kinetic friction between tires and road to be 0.80, calculates the speed of the sports car at impact. what was that speed?