Sorry for posting so many, but I just need to make sure I'm on the right track.
Just need someone to check my working and answers.
A rocket has a mass 3000kg. The fuel used in the rocket has an additonal mass of 500kg. At the launch, the rocket accelerates at 4m/s/s. Using 10m/s/s as gravity.
a) Calculate the net force on the rocket.
f=ma (Newton's 2nd Law)
=3500 x 4
=14000 N
b) What is the weight of the rocket at launch?
w=mg
=3500 x 10
=35000N
c) Determine the upward force exerted by the rocket motors at the instant of the launch
F(net)=W + F(up)
=35000 + (4 x 35000)
=175000N (upwards)
d) The rocket takes 3 minutes to burn all of it's fuel. If the rocket motors suply a constant force, would you expect the acceleration to remain constant during the first 3 minutes. Explain your answer.
No. If the rocket takes 3 mintues to burn all of it's fuel, during that time, the mass of the fuel decreases. Since the force remains the same thorughout the 3 mintues, the rocket will accelerate when there is less mass.
Determine
e) the upward force acting on the rocket after the fuel tank beocme empty.
F(up)=0N
f)the acceleration of the rocket after this instant.
10m/s/s due to gravity.
Check your decimal poing on (c). You went from 14,000 net force to 140,000
d) The acceleration rate increases as the mass (including fuel) decreases
e) is correct. So is (f). Upward thrust ends when the fuel is gone
a) The net force on the rocket can be calculated using Newton's second law, which states that force (F) is equal to mass (m) multiplied by acceleration (a). In this case, the mass of the rocket and the fuel is 3000 kg + 500 kg = 3500 kg, and the acceleration is 4 m/s/s. So, the net force is F = m x a = 3500 kg x 4 m/s/s = 14000 N.
b) The weight of the rocket at launch can be calculated using the formula w = m x g, where w is weight, m is mass, and g is gravity. The mass of the rocket and the fuel is 3500 kg, and the acceleration due to gravity is given as 10 m/s/s. So, the weight of the rocket is w = 3500 kg x 10 m/s/s = 35000 N.
c) The upward force exerted by the rocket motors at the instant of the launch can be determined by subtracting the weight of the rocket from the net force. So, F(up) = F(net) - W = 14000 N - 35000 N = -21000 N (upwards).
d) No, the acceleration is not expected to remain constant during the first 3 minutes. This is because as the rocket burns its fuel, the mass of the rocket decreases. Since force (F) is equal to mass (m) multiplied by acceleration (a), if the force remains constant and the mass decreases, the acceleration will increase. So, the acceleration of the rocket will change throughout the first 3 minutes.
e) After the fuel tank becomes empty, there would be no upward force acting on the rocket from the rocket motors. So, the upward force would be 0 N.
f) After the instant when the fuel tank becomes empty, the only force acting on the rocket would be the force of gravity. Therefore, the acceleration of the rocket would be equal to the acceleration due to gravity, which is given as 10 m/s/s.