# Grade 12 physics projectile concept question

1. Feb 24, 2015

### brandonA

I had a physics lab that is introducing Potential and Kinetic energy into are unit on projectiles. The first question was solve for the impact speed of a projectile launched horizontally at a 13m/s, this impact speed is -14.36m/s. The next question was find the impact speed of the same projectile but it is now launched at an angle of 30 degrees above the horizontal. I understand how to calculate this using kinematic equations but how would I do it with energy, by energy i mean

1/2mv² + mgh = 1/2mv²' + mgh'

Would I need to break it into its components?

2. Feb 25, 2015

### Simon Bridge

You can break it into components if you want - but did you need to break anything into components for the projectile launched horizontally?
In all conservation questions you start by listing the quantities before, and then the quantities after, then you put them equal to each other.
So what kinds of energy does the projectile start with and how much of each?
What kinds of energy does it end up with and how much of each (write down the maths - leaving stuff you don't know as a variable).
before = after ... solve for speed.