This might be an extremely easy question and I'm just over-thinking it, but could someone give me a hand with some grade 10 physics? 1. A downhill skier has an initial speed of 2.5 m/s. She accelerates up to a speed of 20 m/s in 3.8 s. a) Calculate the average acceleration of the skier. Okay, so I know that acceleration equals velocity over time, but I'm slightly confused. So I know how to calculate the acceleration of 20 m/s in 3.8 s. Which is ... (about) 5.26. But, I get stuck here.