1) Newton's second law states that the acceleration of an object is proportional to the force F acting on it, and inversely proportional to its mass m. That is, a=F/m. What are the dimensions of force? 2) A car drives on a highway with a speed of 68 mi/h. What is this speed in km/h? 3) The fastest commercially available rifle bullet claims a muzzle velocity of 4225 ft/s. (a) What is this speed in miles per hour? (b) How far (in meters) can this bullet travel in 5.0 ms? 4) The mass of a newborn baby's brain has been found to increase by about 1.6 mg per minute. (a) How much does the brain's mass increase in one day? (b) How much time does it take for the brain's mass to increase by 0.0075 kg