Acceleration is defined as the rate of change of velocity, or \(\frac {V_I - V_F}{Time}\).

We're given the initial

**and** the final velocities, and also the full time of the collision.

Hence, substitute the values and calculate...

Answer

\(\frac{5-(-2)}{0.20} = 35ms^{-1}\) in a **negative** direction, or *away from the barrier*