For a moving object, the force acting on the object varies directly with the object's acceleration. When a force of 21 N acts on a certain object, the acceleration of the object is 7 m/s^2 . If the acceleration of the object becomes 9 m/s^2, what is the force?
Using the formula for force and acceleration being directly proportional:
F1 / a1 = F2 / a2
Substitute the given values:
21 N / 7 m/s^2 = F2 / 9 m/s^2
Solve for F2:
F2 = (21 N / 7 m/s^2) * 9 m/s^2
F2 = 63 N
Therefore, when the acceleration of the object becomes 9 m/s^2, the force acting on the object is 63 N.