A long line of charge with uniform linear charge density λ1λ1 is located on the xx-axis and another long line of charge with uniform linear charge density λ2λ2 is located on the yy-axis with their centers crossing at the origin. In what direction is the electric field at point zz = aa on the positive zz-axis if λ1λ1 and λ2λ2 are positive?

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?