Q. A car carrying a 75-kg test dummy crashes into a wall at 25 m/s and is brought to rest in 0.1 s. Show that the average force exerted by the seat belt on the dummy is 18, 750 N.
Q. The solution for has a singularity (that is, becomes infinitely large) at a certain angle . For any angle , the expression for will be negative. However, a negative applied force would reverse the direction of friction acting on the lawnmower, and thus this is not a physically acceptable solution. In fact, the increased normal force at these large angles makes the force of friction too large to move the lawnmower at all.