A very light ideal spring with a spring constant (force constant) of 250 N/m pulls horizontally on an 18-kg box that is resting on a horizontal floor. The coefficient of static
friction between the box and the floor is 0.65, and the coefficient of kinetic friction is
0.45. (HINT: Draw free-body diagram with Fs as the force applied)
(a) Draw a free-body diagram of the box labeling all forces acting on it (5 pts)
(b) How long is the spring just as the box is ready to move? (5 pts)
(c) If the spring pulls the box along with a constant forward velocity of 1.75 m/s, how long is the spring? (5 pts)

How does the kinetic energy of a charge change as the charge moves under the effect of an electric field from higher potential to lower potential? a.the kinetic energy increases.b.the kinetic energy decreases.c.the kinetic energy remains the same.d.the kinetic energy is always zero.

Consider a double atwood machine constructed as follows: a mass 4m is suspended from a string that passes over a massless pulley on frictionless bearings. the other end of this string supports a second similar pulley, over which passes a second string supporting a mass of 3m at one end and m at the other. using two suitable generalized coordinates, set up the lagrangian and use the lagrange equations to find the acceleration of the mass 4m when the system is released. explain why the top pulley rotates even though it carries equal weights on each side.

Click the game tab at the bottom of the simulation and select level 1. (there is no seesaw balance for this part of the activity.) balance the first equation, and click check to see if you got it right. if you can’t balance it in the first try, you can try again. work through the five equations for level 1. click continue to go on to level 2, and later level 3. each level is more difficult than the one before. keep trying until all the equations are balanced. in one or two sentences, describe how you did in the balancing game. in a few more sentences, explain one strategy you learned for balancing more complex equations.