A projectile moves at 45° to horizontal after 1 s and horizontally after 2 s. Its initial speed is 10√x m/s. Find x (take g=10 m/s²).
Physics · Mixed Chapter
JEE Main Practice

Question

A projectile moves at 45° to horizontal after 1 s and horizontally after 2 s. Its initial speed is 10√x m/s. Find x (take g=10 m/s²).

G1 Physics · Accepted Answer

Step 1: At t=2 s its vertical velocity is zero, so uᵧ=g×2=20 m/s. Step 2: At t=1 s, vᵧ=uᵧ−g=10 m/s. Its direction is 45°, so horizontal speed uₓ=vᵧ=10 m/s. Step 3: Initial speed u=√(uₓ²+uᵧ²)=√(10²+20²)=10√5 m/s. Step 4: x=5.