How To Know When To Use Which Motion Equation

[justinh8]

Homework Statement

I never know when to use either Distance = Velocity x Time or when to use Distance = v1t + 1/2at^2. Please help me and explain when i have to use which

 

[berkeman]

Homework Statement

I never know when to use either Distance = Velocity x Time or when to use Distance = v1t + 1/2at^2. Please help me and explain when i have to use which

The second equation adds in the last term to account for the effect of a constant acceleration "a". If there is no acceleration, there is no change in velocity. If there is a constant acceleration (like from gravity), you need that extra term.

 

[tiny-tim]

hi justinh8!

they're the same …

if you put a = 0 into s = v₁t + 1/2at²,

you get s = v₁t (which is really s= vt, since v is constant if a = 0)

so you can always use the 2nd one, and you can use the first one if the speed is constant (ie if the acceleration is 0)