Standard +0.3 This is a straightforward projectile motion problem requiring resolution of velocity components and solving a quadratic equation. Students must find when |v| = 18 using v_x = 25cos(50°) (constant) and v_y = 25sin(50°) - gt, then verify the particle is rising. Standard M2 technique with no novel insight required, slightly above average due to the 'rising' condition check.
1 A particle is projected with speed \(25 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) at an angle of \(50 ^ { \circ }\) above the horizontal. Calculate the time after projection when the particle has speed \(18 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) and is rising.
1 A particle is projected with speed $25 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ at an angle of $50 ^ { \circ }$ above the horizontal. Calculate the time after projection when the particle has speed $18 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ and is rising.\\
\hfill \mbox{\textit{CAIE M2 Q1 [4]}}