Three simple physics questions

1. Time taken to reach the target = 1700/500 s = 3.4 sConsider the vertical motion, use equation of motion: s = ut + (1/2)at^2with u = 0 m/s, t = 3.4 s, a = -g (= -10 m/s2), s =?hence, s = (1/2)(-10)(3.4)^2 m = 57.8 m The target is missed by 57.8 m 2. 40 mph = 17.88 m/s50 feet = 15.24 m (I presume that this is the radius)hence, centripetal acceleration = 17.88^2/15.24 m/s2 = 21 m/s2 = 2.1g (take g = 10 m/s2) 3. 200 lb = 90.9 kg The acceleration due to gravity on earth g = GM/R^2where G is the Universal Gravitational Constant, M is the mass of the earth, and R is the radius of the earth. Mass of planet M’ = 4.5MVolume of planet = (4/3).(pi).(R’)^3 = 6[(4/3)(pi)(R^3)]where R’ is the radius of the planet, and pi = 3.14159…Hence, R’ = (6)^(1/3).R = 1.817R The acceleration due to gravity on the planet g’ = GM’/(R’)^2 = G(4.5M)/(1.817R)^2g’ = [4.5/1.817^2].(GM/R^2) = [4.5/1.817^2]g = 1.363g = 13.63 m/s2 (take g = 10 m/s2)Weight on planet = 90.9 x 13.63 N = 1240 N (or 124 kgf, or 273 lb)