Final answer:
The force needed to accelerate a 4kg skateboard at 3m/s2 is 12N.
Step-by-step explanation:
To calculate the force needed to accelerate an object, we can use Newton's second law of motion. According to this law, the force (F) is equal to the mass (m) of the object multiplied by its acceleration (a). So, in this case, the force needed to accelerate the 4kg skateboard at 3m/s2 would be:
F = m * a
F = 4kg * 3m/s2
F = 12N
Therefore, a force of 12 Newtons is needed to accelerate the 4kg skateboard at 3m/s2.