A mover pushes a 255 kg piano with a 77.5 N force to the left, while
a second mover pulls the piano
48.7 N to the left. What is the
acceleration of the piano?
(Watch your minus signs.)
(Unit = m/s2)

Explanation:

According to the newton's second law of motion we can apply F=ma hear

Force = mass * acceleration

(assume the piano is moving left side )

←F = ma

d. platinum would have the greatest temperature increase because it has the lowest specific heat.

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.