Q.

A particle starts from origin at t=0 with a velocity 5i^ m/s and moves in x-y plane under action of a force which produces a constant acceleration of (3i^+2j^)m/s2. If the x-coordinate of the particle at that instant is 84 m, then the speed of the particle at this time is αm/s. The value of α is ____________ .                 [2024]


Ans.

(673)        Given, ux=5 m/s,ax=3 m/s2 and x=84 m

                 Using, vx2-ux2=2ax

                 vx2-25=2(3)(84)vx=23m/s

                 vx-ux=axtt=23-53=6s

                 vy=0+ayt=0+2×(6)=12m/s

                  v2=vx2+vy2=232+122=673

                 v=673m/s