# A spring is suspended on the ceiling of a truck, find acceleration?

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1. Oct 3, 2015

### greenglasses

1. The problem statement, all variables and given/known data

A massless spring with a spring constant k = 500 N/m is suspended from a hook on the ceiling of a cargo truck moving in a straight line (horizontally) on the highway. A child reaches over from her seat and suspends a 1.1 kg toy on the free end of the spring. The child notices that the spring is now 5.0 cm longer than when it was hanging freely. Find the acceleration for the truck.

2. Relevant equations

Fk = -kx
Fnet = ma

3. The attempt at a solution

I honestly have no clue what to do since the spring force is in the vertical direction but the truck is accelerating horizontally. Would appreciate any pointers in the right direction.

2. Oct 3, 2015

### billy_joule

Draw a free body diagram. The weighted spring will not remain vertical when the truck is accelerating. The greater the acceleration, the greater the spring extends and the greater the springs angle wrt vertical becomes.