Importance of liquid pressure

Acar travels along a highway with a velocity of 24 m/s, west. the car exits the highway; and 4.0 s later, its instantaneous velocity is 16 m/s, 45° north of west. what is the magnitude of the average acceleration of the car during the four-second interval?

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?

Due in 40 explain in terms of frame of reference if you’re inside a moving train everything on the outside can seem to be moving