Question

What is the direction of acceleration ?

Answer 1

depends on the direction of the velocity :)

Answer 2

@Chibi_Robo3 no, it depends on the direction of the CHANGE of the velocity. As a counterexample, just think of a man stepping on the break of a car. The velocity is still going forward, but the acceleration is backward

Answer 3

The acceleration is in the direction of the resultant force.

Taking all forces acting on the body, they can be resolved into 1 equivalent resultant. The acceleration will be in the direction of that force.

As @alias says the velocity may be in a completely different direction.
Take another example- A mass rotating attached to a string. The acceleration is towards the centre of the circle (in the direction of the tension in the string) but the velocity is a circular arc and is tangential to the circle at all times. (i.e. the body does not move in the direction of the force - but it does ACCELERATE in that direction)

Answer 4

Kudos to you sir/madam :)