Question

why we lean forward when brake apply and why we lean backward when a car accelerates

Answer 1

when we are sitting in a car and car. comes in motion our body also comes in. motion but when the brakes are applied the car stopped but aur Body remains in. motion that's why we fall forward and when the the car Is at the rest aur body is also comes in rest but when the car comes in motion aur body remains at rest that's why we fall backward

hope this helps ☺☺

Answer 2

when we apply brake cars velocity suddenly decreases but it doesn't stop the drivers velocity so we lean forward.
when we accelerate then car's velocity suddenly increases but drivers velocity is normal so he/she lean back.
I hope it helped you