My FPS improves when i disable collision, what does this mean?

When i play BEAMNG drive, it has very low fps (feels like 10) on the lowest setting with collision activated. But when i deactivate collision it spikes to about 40 fps. What does this mean? It doesn't seem to be using even 20% of CPU (according to task manager) when collisions are on. It also only takes up upto 2GB ram.

My specs are:
8gb ram, Win 10, Nvidia geforce gt 740m and intel icore 7 quad processor(2.2ghz). I am using a laptop.