The speed of the car at the bottom of the dip given the parameters in the equation is; v = 7 m/s
Since the motion is circular, it means that the acceleration of the car will be acting towards the centre of the circle and as a result the acceleration will be acting upwards with the formula; a = v²/r
Now, if the mass of a passenger is denoted as m, then the net force on the passenger will be;
F = mv²/r
Also, in the roller coaster, two other forces are acting which are the force of gravity(F_g) acting downward and also the force of the seat(F_seat) acting upwards. Thus, from equilibrium of forces, we can say that;