I'm doing Salters Horners at the moment and did my coursework a few months ago. Don't worry too much, I found a lot of good resources online to get ideas from.
Here’s a list of experiments I and my friends did -
> Projectile motion (a good excuse to build an onager)
> Force of recoil from a catapult (a catapult on wheels and different masses basically)
> Finding the natural frequency of a building (theoretical and the practical)
> Capacitors in AC and DC circuits (including AC theory)
> Investigating flow rates (a bucket of water and different sized tubes out of the bottom)
> Investigating how high a ball bounces (depending on height, mass etc)
Don't overcomplicate something, like I nearly did and strayed into degree level physics. Also don't do something too simple, my friend ended up investigating AC theory with capacitors as his was too simple. Choose one that you can draw a certain conclusion from and just follow the specification. If you want to bump your marks up some more, develop the conclusions using all your scientific knowledge.
I screwed up on my exams last year but still managed to get a C as my coursework was an A. I'm beginning to like the idea of coursework now
just not looking forward to the re-sits on Thursday lol. Also, don't forget that this year it only makes up 10% of your final grade.