1. The problem statement, all variables and given/known data The resistance to motion of a projectile, of mass m, is proportional to its speed. When falling vertically its terminal velocity is 19.6 m/s. The projectile is thrown vertically upwards with gravity acting downwards. (a) Assume that the resistance to motion can be expressed as kv where v is the velocity andk is a constant. Determine k in terms of m using the terminal velocity value 19.6 m/s. (b) Assume that the projectile is launched vertically upwards with a speed of 6 m/s. Write down the equation of motion which describes the resulting motion and find the expression for the velocity, v, at time t. 2. Relevant equations 3. The attempt at a solution a) I think I've got part (a) correct. I did g/19.6 = k, therefore constant k = 1/2 b) My biggest problem with this question is working out the resultant force. The way I would attempt this question is work out the resultant force and then use the equation F=ma. I would substitute a=dv/dt and then simply solve the differential equation by making v the subject. However I can't seem to work out what F would be. I know that you would have to subtract mg (weight) from the projectile force. My attempt would be mkv-mg=ma kv-g=dv/dt Thank you so much for your help!