1. The problem statement, all variables and given/known data In a test of a car seat belt system, a dummy of mass 55kg in a car seat is accelerated to a speed of 35m/s before it hits a brick wall. The seat belt allows the dummy to move forward relative to the seat by a distance of 0.60 m. Calculate, (a) The deceleration of the dummy (b) The force on the dummy due to the seat belt 2. Relevant equations F=ma F=p/t F=mdv/dt 3. The attempt at a solution I thought of using simultaneous equation to solve this. When I substituted the values to the equation F=ma, I realised F is an unknown. Then, time is also an unknown.