Convert the value of g=9.8m/s^2 into km/hr^2

What can you increase the strength of an electromagnet by

An astronaut in space cannot use a scale or balance to weigh objects because there is no gravity. but she does have devices to measure distance and time accurately. she knows her own mass is 77.4 kg , but she is unsure of the mass of a large gas canister in the airless rocket. when this canister is approaching her at 3.50 m/s , she pushes against it, which slows it down to 1.30 m/s (but does not reverse it) and gives her a speed of 2.60 m/s . what is the mass of the canister?

Efficiency is the ratio of to for a system a)power in to power in b)power in to power out c) power out to power out d) power out to power in