During a lift off , the thrust a rocket produces must overcome the force of gravity in order to lift the rocket off the ground. If a rocket with a mass of 5kg produces a force of 180N, how fast will the rocket be travelling 3 seconds after ignition?

First calculate the acceleration.

a = (Thrust-Weight)/M = (180-M*g)/M
180/5 -g = 26.2 m/s^2

Assume the mass remains the same (although it actually must decrease as propellant is released) and use

Y = (1/2) a t^2
to compute how far it rises (Y) in t=3 seconds.

I just noticed they asked for the velocity after three seconds, not the distance.

Use V = a t for velocity.

thank you drwls

To determine how fast the rocket will be traveling 3 seconds after ignition, we need to apply Newton's second law of motion, which states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

First, let's calculate the acceleration of the rocket using Newton's second law:

Acceleration (a) = Net Force (F) / Mass (m)

Given: Net Force (F) = 180N
Mass (m) = 5kg

Substituting the values into the equation:
a = 180N / 5kg
a = 36 m/s²

Now, we can use the formula for acceleration to determine the velocity of the rocket after 3 seconds.

Velocity (v) = Initial Velocity (u) + (Acceleration (a) * Time (t))

Since the rocket starts from rest (initial velocity is 0 m/s), the equation simplifies to:

Velocity (v) = Acceleration (a) * Time (t)

v = 36 m/s² * 3s
v = 108 m/s

Therefore, the rocket will be traveling at a speed of 108 m/s 3 seconds after ignition.