<u>Answer:</u> The force that must be applied is 15 N.
<u>Explanation:</u>
Force exerted on the object is defined as the product of mass of the object and the acceleration of the object.
Mathematically,
where,
F = force exerted = ?
m = mass of the object = 3 kg
a = acceleration of the object =
Putting values in above equation, we get:
Hence, the force that must be applied is 15 N.