Question

A 10,000 kg spaceship decelerates uniformly to reduce its speed from 3,500 km/h to 1,700 km/hr in 1 s. what net force acted on this spaceship

Answer 1

First, let's calculate the initial and final speed of the spaceship:
$v_i = 3500 km/h = 972.2 m/s$
$v_f = 1700 km/h = 472.2 m/s$

By using the initial and final speed, we can calculate the acceleration of the spaceship:
$a= \frac{v_f-v_i}{t}= \frac{472.2 m/s-972.2 m/s}{1 s}= -500 m/s^2$
where the negative sign means it is directed against the motion of the spaceship (in fact, the spaceship is decelerating).

And now, by using Newton's second law:
$F=ma$
we can calculate the net force that acted on the spaceship:
$F=(10000 kg)(-500 m/s^2)=-5 \cdot 10^6 N$
where the negative sign means it is directed against the direction of motion of the spaceship.