Below are some common student difficulties experienced in solving problems:

Students often fail to see the kinematical constraint of a string connecting two accelerating objects. (description) (discover) (references)

Students who do well in quantitative problem solving have difficulties with purely conceptal problems. (description) (discover) (references)

Students fail to see acceleration as the ratio Dv/Dt. (description) (discover) (references)

Students use compensation arguments to incorrectly solve conceptual problems. (description) (discover) (references)