Finding the upward force acting on an object

[shootingrubbe]

Homework Statement

A spaceship is accelerating upwards with an acceleration of 0.50g. It's mass is 2.0 x 10⁶ kg. What is the upward force this object is exerting?

Homework Equations

Fnet = ma
Fnet = Sum of all forces.

The Attempt at a Solution

A = 4.9 m/s² [up]
g = 9.8 m/s² [down]
m = 2.0*10⁶ kg.

I plugged it into the Fnet = ma. So:
Fnet = (2.0*10⁶ kg)(4.9 m/s² [up])
= 9800000 N [up]

Then, I found the force of gravity acting on the object... It just would be 2(9800000 N) because the acceleration I just used was half that of gravity. The force of gravity acting on the object would be 19600000 N [down].

So: Fnet = Fup + Fg
9800000 N = Fup +(-19600000 N)
9800000 N = Fup - 19600000 N
Fup = 9800000 N + 19600000 N
= 29400000 N [up]
= 2.9 * 10⁷ N [up]

Can anyone let me know if I did this correctly or if I am totally off?

Thanks.

 

[LowlyPion]

Since you are using the word upward I would have to agree that gravity is involved.

If it is moving against gravity, then isn't it simply

F = m*a = m*(g + .5g) = 3/2*m*g ?

This apparently agrees with your result.

 

[nlightner]

Your solution is correct! You correctly used the equation Fnet = ma to find the net force acting on the object, which in this case is equal to the upward force since the object is accelerating upwards. You then correctly found the force of gravity acting on the object, which is equal to its weight. Finally, you used the fact that the net force is equal to the sum of all forces to find the upward force, which is equal to the net force minus the force of gravity. Good job!