Consider the acceleration of an object that is undergoing simple harmonic motion. is this acceleration zero or nonzero?

Non-zero

Explanation:

For a simple harmonic motion, the restoring force is given by

F = -kx (1)

where

k is the spring constant

x is the displacement of the system with respect to the equilibrium position

According to Newton's second law, the acceleration of the system is given by

a = F/m (2)

where

m is the mass of the system

So if we substitute (1) into (2) we find

a = -kx/m

so the acceleration is directly proportional to the displacement. Since the value of the displacement  in a simple harmonic motion constantly changes, the acceleration changes as well, so it is non-zero (apart from the instant where the displacement is zero, x = 0, when the acceleration is also zero)

what was the acceleration of the 2 kg cart?

⇒ 16.0 cm/s2

what was the acceleration of the 4 kg cart?

⇒ 8.1 cm/s2

what was the acceleration of the 6 kg cart?

⇒ 5.3 cm/s2

the answer is b, have negligible mass