Two particles a and b, move with constant velocities →v1 and →v2. at the initial moment their position vectors are →r1 and →r2 respectively. the condition for particles a and b for their collision is :

(1)vector r1 - vector r2 = vector v1 - vector v2

(2)vector r1 - vector r2/magnitude of (vector r1 - vector r2 ) = vector v1 - vector v2/ magnitude of (vector v1 - vector v2)

(3)vector r1 . vector v1 = vector r2 . vector v2

(4)vector r1 x vector v1 = vector r2 x vector v2

The magnetic field inside a superconducting solenoid is 4.50 t. the solenoid has an inner diameter of 6.20 cm and a length of 26.0 cm. determine (a) the magnetic energy density in the field and (b) the energy stored in the magnetic field within the solenoid.

What’s #16 asking me and how do i solve it?

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?