Question

You may use your text, notes, a computer, and/or a calculator. Ignore significant figures. Solutions will be posted on D2L within 48 hours. Each problem is worth. An astronaut on board a spacecraft is in orbit around the Earth in uniform circular motion. Answer the following with brief (1-2 sentence) explanations: (a) Is her velocity constant? (b) Is her speed constant? (c) Is her acceleration constant? In the bloodstream, an erythrocyte (red blood cell) of mass m moves with velocity v to the right. It collides head-on with a leukocyte (white blood cell) of twice its mass, moving to the left with three times its speed. After the collision, they become stuck together, (a) Sketch the system before and after the collision, and (b) Compute the final velocity v_f of the combined cells after the collision in terms of v. Assume no external forces act on the erythrocyte-leukocyte system. A certain mass of water at the top of Niagara Falls has a temperature of +10.0 degree C. It falls a distance of 50 m. Assuming that all its potential energy is converted into thermal energy, calculate the temperature of the mass of water at the bottom of the falls. In the figure below, a spring with k = 1400 N/m is firmly anchored to the bottom of the Laurentian swimming pool. A diver in Hill SCUBA gear (shown as colored box) with total mass 100 kg and density of 0.65 g/cm3 holds on to the top of the spring. The system reaches a new static equilibrium, shown in the figure at right, after the spring is elongated by a length deltaL. a) Draw a free body diagram for the diver

Answer 1

1. a. Her velocity is not constant as the direction of motion along the circular path is changing at every moment.

b. In a uniform circular motion, the speed is constant.

c. The object accelerates because of change in direction of velocity vector and acceleration is directed inwards. This is equal tot he centripetal acceleration a = v^2/r. Since the velocity is squared in this expression, hence the direction of velocity has no effect on the circular motion and therefore, the acceleration is constant.