A particle moves in the xy-plane according to x=3t and y=25-4t, with x and y in metre. Find the minimum distance of the particle from the origin, in metre.

Question

G1 Physics · Accepted Answer

Distance from origin satisfies r²=x²+y²=(3t)²+(25-4t)²=25t²-200t+625=25[(t-4)²+9]. This is minimum at t=4 s, so rₘᵢₙ²=25×9 and rₘᵢₙ=15 m.