# A projectile is launched at an angle of 30 degrees.a) is there any point on the trajectory where vector v and vector a are parallel to each other? If so, where? b) is there...

A projectile is launched at an angle of 30 degrees.

a) is there any point on the trajectory where vector v and vector a are parallel to each other? If so, where?

b) is there any point on the trajectory where vector v and vector a are perpendicular to each other? If so, where?

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### 1 Answer

a) You should remember that if the projectile is launched at an angle of `90^o` , the horizontal component `bar v_x` vanishes and acceleration hat a becomes parallel to `bar v` .

**Since the problem provides the information that the projectile is launchedat an angle of `30^o` , then vector `bar a` and `bar v ` are not parallel at any point of the trajectory.**

b) You should know that gravity makes acceleration to act downward, hence, the direction of the horizontal component `bar v_x` needs to become parallel to x axis for `bar a _|_bar v` .

**Notice that the position of component bar `v_x` at the top of trajectory is parallel to x axis, hence `bar a` is perpendicular to `bar v` .**