an arrow is fire with a speed of 20.0m/s at a block of Styrofoam resting on a smooth surface. The arrow penetrates a certain distance into the block...

an arrow is fire with a speed of 20.0m/s at a block of Styrofoam resting on a smooth surface. The arrow penetrates a certain distance into the block before coming to rest relative to it. During the process the arrow's deceleration has a magnitude of 1550m/s2 and the block's acceleration has a magnitude of 450m/s2. How long does it take for the arrow to stop moving with respect to the block?