An 90.3-kg astronaut steps onto the surface of a 1.7*10^27-kg planet. If the radius of the planet is 6.1*10^7m, the force of gravity experienced by the astronaut is N. Write your answer in scientific notation and round your answer to three significant figures.

Aresistor with an unknown resistance is connected in parallel to a 9 ω resistor. when both resistors are connected in parallel to an emf source of 21 v, the current through the unknown resistor is measured with an ammeter to be 4 a. what is the resistance of the unknown resistor? answer in units of ω.

Achild has maximum walking speed of 1.6 m/s. what is the length of the child's legs? 0.26 m

Which of the following can enter and exit a closed system? a. matter and energy b. neither energy nor matter c. matter but not energy d. enrgy but not matter