newton's law of motion

Question

A fully loaded Saturn V rocket has a mass of 2.92 x 106 kg. Its engines have a thrust of 3.34 x 107 N.

a. What is the downward force of gravity on the rocket at blast-off?

b. What is the unbalanced force on the rocket at blast-off?

c. What is the acceleration of the rocket as it leaves the launching pad?

d. As the rocket travels upwards, the engine thrust remains constant, but the mass of the rocket decreases. Why?

e. Does the acceleration of the rocket increase, decrease, or remain the same as the engines continue to fire?

Answer 1

Mass_(rocket) = 2.92 x 10⁶ kg. F_thrust = 3.34 x 10⁷ N.

a. What is the downward force of gravity on the rocket at blast-off?

W = Mg = 2.92 x 10⁶ x 9.8 = 28,616,000 N (-ve for down)

b. What is the unbalanced force on the rocket at blast-off?

F_net = F_thrust - W = 33,400,000 - 28,616,000 = 4784000N

c. What is the acceleration of the rocket as it leaves the launching pad?

a = F_net / M = 4784000 / 2920000 kg =~ 1.64 m/s²

d. As the rocket travels upwards, the engine thrust remains constant, but the mass of the rocket decreases. Why?

Because it consumes fuel and mass burns into energy for thrust.

e. Does the acceleration of the rocket increase, decrease, or remain the same as the engines continue to fire?

a = Fnet /M while Since W gets less, Fnet = Fthrust - W = F(net) gets more and more and mass decreases. So, accelerations constantly increase at an increasing rate.