# 3 different types of vertical projectile motion

3 different types of vertical projectile motion are:

1)Vertical downward projection from a starting point above the ground–

– In this case, the object can be dropped (Initial velocity = 0)

– or it can be thrown downwards at an initial velocity >0

2)Vertical Upward Projection from a starting point at the ground level; the object turns around and returns to the starting point.

3)Vertical Upward Projection from a starting point above the ground; the object goes to the highest point and then turns, and moves downwards past the starting point towards the ground.

**Signs of velocity, displacement, and g**

Here, we will use these signs for understanding: V_{i} and V_{f} are the initial and final velocities respectively

**Case 1: Vertical downward projection from a starting point above the ground **

If the object is dropped then: V

_{i}= 0 and V_{f}= positive

Downward displacement: Positive

g=9.8 m/s^{2}

If the object is thrown downward then: V

_{i}= positive and V_{f}= positive

Downward displacement: Positive

g=9.8 m/s^{2}

**Case 2: Vertical Upward Projection from a starting point at the ground level; the object turns around at the highest point and returns to the starting point**

Considering the upward direction as positive, and the downward direction as negative:

V_{i}= positive and V_{f}= negative

V_{f}= – V_{i}

Net displacement: zero

g= – 9.8 m/s^{2}

Considering the upward direction as negative, and the downward direction as positive:

V_{i}= negative and V_{f}= positive

V_{f}= – V_{i}

Net displacement: zero

g= + 9.8 m/s^{2}

**Case 3: Vertical Upward Projection from a starting point above the ground**

Considering the upward direction as positive, and the downward direction as negative:

V_{i}= positive and V_{f}= negative

Net displacement: negative*

g= – 9.8 m/s^{2}

Considering the upward direction as negative, and the downward direction as positive:

V_{i}= negative and V_{f}= positive

V_{f}= – V_{i}

Net displacement: positive*

g= + 9.8 m/s^{2}

* The starting point can be taken as the reference point (zero).

If this is so, then a displacement below the starting point will have the same sign as the downward motion. A displacement above the starting position will have the same sign as the upward motion.