Newton's Laws Legacy Problem #8 Guided Solution

The traits of a good problem solver are to carefully read a problem, identifying the known and the unknown information in terms of variables, and then plotting a strategy to get from that known information to the unknown information. None of that involves a calculator, and that's where most of the work takes place. So here, what we're told is a person on the top-thrilled dragster accelerates from 0 to 54 meters per second in 3.8 seconds. And what we're asked to calculate is the net force on this 86 kilogram man. So as I look at this, I have to focus on the accelerating phase, the launching system of this coaster, where the initial speed is 0, V0 is 0, VF is 54 meters per second, and the time to go from the V0 to the VF is 3.8 seconds. Together that's information about finding acceleration. Finally I know that M equals 86 kilograms. What I'm asked to calculate is the net force, F net equal question mark. So as I go to think about this, my strategy planning phase involves thinking about equations that relate knowns and unknowns. I know, because it's one of the fundamental equations in this unit, that F net equals MA. And I can calculate F net if I can just get my A value. The mass is given as 86 kilograms. So you have to ask yourself, what's in this problem that allows me to calculate A? And what is present is a delta V of 54 for a time of 3.8. And the acceleration, the rate of change of velocity, is the delta V over T. So take the 54 and divide by the 3.8, and that gives you an acceleration in meters per second per second. Multiplying acceleration by mass in kilograms gives you a net force in newtons.