AP Physics 1 is probably the hardest AP class you can take that has the lowest passing rate of 51.6%. This means that about half the students who take up the course tend to fail the 3 hour exam. However, AP Chemistry is also hard as it falls under the top 3 hardest AP classes there is. In the end, it really depends on the student because some people find physics easier than chemistry and some, vice versa. A good grade to get in AP Physics can be 3 or above since a 3 would get you college credit when you apply to university.