Question

Chapter D3, Problem D3/149 The 174-kg lunar lander is descending onto the moon's surface with a velocity of 5.0 m/s when its retro-engine is fired. If the engine produces a thrust T for 3.2 s which varies with the time as shown and then cuts off, calculate the velocity of the lander when t = 3.9 s assuming that it has not yet landed. Gravitational acceleration at the moon's surface is 1.62 m/s2. The velocity is positive if moving downward, negative if up. 5.0 m/s 8 TAN 702 0 0 1.6 3.2 Answe: V = m/s the tolerance is +/-2%

Answer 1

Solº 3 me 17419 5 mis v V2 cet t=3.9 see Im = 1.62 misa o som Et dt =mov 13.9 3.2 fimo tp bus Tdt mi U2 - V) 0 0 (Arey yn der Reinve). mg [tb. M1212) 'D - 174x 1.62 x 3-9 H x 16 x 702 + 1.6x70 **$*7027 174 (V2-5) |v2 = 1.635 mis Ila * so, velocity ler t=3.9 see is a 1.635 mis