4. since astronauts in orbit are apparently weightless, a clever method of measuring their masses is needed to monitor their mass gains or losses to adjust diets. one way to do this is to exert a known force on an astronaut and measure the acceleration produced. suppose a net external force of 50.0 n is exerted and the astronaut’s acceleration is measured to be 0.893 m/s2. (a) calculate her mass. (b) by exerting a force on the astronaut, the vehicle in which they orbit experiences an equal and opposite force. discuss how this would affect the measurement of the astronaut’s acceleration. propose a method in which recoil of the vehicle is avoided.