Large objects have inertia and tend to keep moving-Newton's first law. Life is very different for small microorganisms that swim through water. For them, drag forces are so large that they instantly stop, without coasting, if they cease their swimming motion. To swim at constant speed, they must exert a constant propulsion force by rotating corkscrew-like flagella or beating hair-like cilia. The quadratic model of drag given by the equation, Ď= (CpAv², direction opposite the motion), fails for very small particles. Instead, small object moving in a liquid experiences a linear drag force, D= (bu, direction opposite the motion), where b is a constant. For a sphere of radius R, the drag constant can be shown to be b = 6R, where is the viscosity of the liquid. Water at 20°C has viscosity 1.0 x 10-³ N-s/m². The propulsion forces are very small, but so are the organisms. To judge whether the propulsion force is large or small relative to the organism, compute the acceleration that the propulsion force could give each organism if there were no drag. The density of both organisms is the same as that of water, 1000 kg/m³. Part C Compute the acceleration that the propulsion force could give the paramecium if there were no drag Express your answer to two significant figures and include the appropriate units. ► View Available Hint(s) a= Submit Part D Value a 4 Value Compute the acceleration that the propulsion force could give the E.coli bacterium if there were no drag. Express your answer to two significant figures and include the appropriate units. ▸ View Available Hint(s) Units 4 → ? Units ?

Three objects are connected as shown in the figure.  The strings and frictionless pulleys have negligible masses.  The coefficient of kinetic friction is 0.25 and static friction is 0.30.  Block A has a mass of 3 kg and block B has a mass of 4 kg.  a) What is the maximum mass block C can have before block B will start to move?  b) If block C has a mass of 7 kg. and was 1 m above the ground, how long would it take block C to hit the ground starting from rest?

A 40 N box is resting on a table when a 20 N force is applied to it horizontally. The coefficients of static and kinetic friction are 0.3 and 0.1, respectively. Which of the following best describes the resulting motion of the box?    The motion of the box cannot be determined with the given information.      The box accelerates in the direction of the applied force.      The box remains at rest.      The box moves with a constant velocity in the direction of the applied force.

This problem has been removed by your teacher and will not affect your score. A 75kg bicyclist (including the bicycle) is pedaling uphill with a speed increasing at a rate of 1.7m/s?. The bicyclist is also experiencing a 20N drag. Neglect any friction impeding her motion. How many forces are acting on the bicyclist? Are all forces on the bicyclist balanced? What is the magnitude of the net force on the bicyclist? unit 13° What is the magnitude of the normal force on the biyclist? unit How much force is she generating by pedaling? unit cam be d check answers

(a) After J. J. Thompson experimentally discovered the existence of electrons in 1897, he went on to propose the plum pudding model of matter. What was the plum pudding model? What did Ernest Rutherford conclude about the structure of matter based on his experimental results from bombarding gold foil with alpha particles? (b) What was the proposed atomic model of matter put forward by Rutherford? Theoretically what was the problem with his proposed model of the atom? (c) What was the modification made by Niels Bohr to Rutherford's model, i.e., what were the assumptions that Bohr made for his version of the atomic model of matter? (d) What observational phenomena was Bohr's proposed model able to explain? How did his model explain these phenomena? (e) Draw an energy level diagram with one representative transition to support your answer to part (d).

You push downward on a trunk at an angle 25° below the horizontal with a force of  750N If the trunk is on a flat surface and the coefficient of static friction between the surface and the trunk is 0.61, what is the most massive trunk you will be able to move?     93 kg     81 kg     112 kg     73 kg

At Ted's request, Bill pushes the pizza box across the granite countertop towards Ted. When the box leaves Bill's hand it is sliding at 2.60 m/s. The box comes to rest over a distance of 110 cm. What is the coefficient of kinetic friction, uk, between the pizza box and the countertop? (Ignore air drag.)