A box **(550 kg)** sits inside the trailer of a semi truck at a stoplight. When the light turns green, the driver accelerates at a constant rate. The coefficient of **static friction µ _{s} = 0.7** between the box and the floor of the trailer. Assume g = 10 m/s

^{2}.

a) When the truck is **accelerating to the left**, what is the **direction** of the **friction** force on box 1 (right, left, or none)?

b) What is the **maximum magnitude** of the static **friction** force holding box 1 in place?

N

c) What is the **maximum magnitude** of **acceleration** the truck can have such that box 1 does not slip?

m/s^{2}