A particle of mass 5 kg moves in the xy-plane with potential energy U=(-7x+24y) J. Initially it is at the origin with velocity u⃗=(14.4î+4.2ĵ) m/s.
Select all that apply

Question

A particle of mass 5 kg moves in the xy-plane with potential energy U=(-7x+24y) J. Initially it is at the origin with velocity u⃗=(14.4î+4.2ĵ) m/s.

G1 Physics · Accepted Answer

F⃗=-∇U=7î-24ĵ N, so a⃗=(1.4î-4.8ĵ) m/s² with magnitude 5 m/s². u⃗·a⃗=14.4(1.4)+4.2(-4.8)=0, so C is true. After 4 s, v⃗=(20î-15ĵ) m/s and speed=25 m/s, so A is true. Hence A,C.