help with net force

Question

if a net force of 10 N accelerates an object at the rate of 2 m/s^2, what will be the acceleration if the net force is  30 N?

 

a.  10 m/s^2

b.   30 m/s^2

c.  6 m/x^2

 

 

with a force of 50 N,  Janet is pushing a heavy box across a floor at constant velocity.  From this information we can conluce that

 

a.  the box is in equilibrium

b.  the force of friction on the box is 50 N

c.  the box is not accelerating

d.  all of these

 

thanks

Answer 1

for the first question we know that F = ma. For the first part, 10N/(2m/s^2) gives a mass of 5kg. Now using F = ma again but rearranging for acceleration (F/m = a) we find that 30N/5kg will give an acceleration of 6m/s^2 -- c.

 

All of these are true. If Janet is pushing with 50N of force and it is moving at a constant velocity (a = 0, letter c) then we know that that force must be balanced by another equal and opposite force so that the sum of forces adds to zero, which means zero acceleration and constant velocity. Being in equilibrium means that the sum of forces is zero (part a). The force that must balance the 50N force must be friction, which is both equal and opposite (part b). All three work: d.