A heavy block, labeled "A", is sitting on a table. On top of that block is a lighter block, labeled "B" as shown in the figure at the right. Consider three cases. (A) The finger is pushing but not hard enough. Neither block moves. (B) The finger is pushing hard enough that the two blocks are speeding up. (C) The blocks have sped up, and are now moving at a constant speed. The finger still has to push to keep them going at a constant velocity. B A In all cases where the blocks are moving, they are moving together. (Block B is not sliding on block A.) Block A has a mass of 0.6 kg; block B has a mass of 0.1 kg. the coefficient of friction between the block and the table is 0.3 and the coefficient of riction between the two blocks is 0.2. (You may use g = 10 N/kg and you may treat kinetic and static friction as the same.) 1. For case (A), what is the maximum force the finger can exert without the blocks beginning to move? 2. For case (B), while the blocks are speeding up, the finger is pushing with a force of 3.5 N. Can you find the acceleration of plock A? If so, find it and show your work. If not, explain why not. 3. Find the time At needed for this force to bring the block from rest to a speed of 10 cm/s. 3. For case (B), we are assuming that the blocks are moving together. This means that block B is speeding up. But the finger s not touching block B. What force is responsible for the acceleration of block B? Find its magnitude and direction. Is our assumption correct? Will block B indeed be able to speed up with block A without slipping? Explain. 4. Suppose the bottom block has a mass of 0.4 kg and the top block has a mass of 0.1 kg What force do you need to exert to keep the blocks moving at a constant speed of 10 cm/s?

This problem pertains to the diagram on the right.  Two dock workers pull a 1500 kg boat.                  a)  What is the sum of force A and force B? Give the x and y components, in units of Newtons.                b)  What is acceleration of the boat? Give the x and y components, in units of m/s2.                c)  What is the magnitude of the boat’s acceleration, in units of m/s2?                d)  What is the direction of the boat’s acceleration? Give your answer as an angle measured relative to the x axis.

A skyscraper window washer is standing on a 6 kg plank that is 3 m long, and that is supported by two vertical cables, one at each end.  If the window washer has a mass of 80 kg and is standing 2 m away from the cable on her left, what is the tension in the cable on her right? (Note that in the diagram, the window washer is facing into the screen.)

Write the position equation Xa(t) describing the motion of body A graphed in the figure at right.Write the position equation Xb(t) describing the motion of body B graphed in the figure

You hang a light in front of your house using an elaborate system to keep the 12-kg object in static equilibrium (Figure 1). What are the magnitudes of the forces that the ropes must exert on the knot connecting the three ropes if θ2 = 63∘ and θ3 = 45∘?

Imagine you are learning to drive and you get into your parent/guardian's vehicle to practice. All you see in the rearview mirror is the back seat. Why does this happen?

The four cases above show four pucks (viewed from above) sliding to the right on a smooth table. Each puck collides with and sticks to a rod that can move or rotate with negligible friction. In all four cases, the pucks are identical, the rods are identical, the initial rightward velocities of the puck are identical, and the initial velocities of the pucks are perpendicular to the rods' lengths. In Cases A and D, the rod is fixed to the table by a pin with negligible friction, but in Cases B and C, the rod is free to move. Cases A and C, the puck collides with the center of the rod. In which case is Linear Momentum NOT conserved. Answer two if needed. In Case A Case B Case C Case D a

In the figure at the right is shown three graphs of the shapes of the same taut elastic string in three different circumstances, labeled A, B, and C. In some of the problems below, the string represents a guitar string, tied down at both ends, while in others, it is part of a very long telephone wire whose ends are not shown. Be careful to note which is which for each problem! The string is light enough that the effects of gravity can be ignored. In each case, the bit of string at the position x = 23 cm is painted blue. 4. Suppose that graph C represents part of a long wire, under tension, and is showing a left traveling wave at a particular instant. What can you say about the velocity of the blue bead in case C at the instant shown? a. It is upward. b. It is downward.     c. It is 0. d. You can’t say anything from the information given. 5. Suppose that graph C represents part of a long wire, under tension, and is showing a left traveling wave at a particular instant. What can you say…

Figure 3 L Before d. X2 After An orange block of mass 2.14 kg is on an inclined plane. There is no friction between the block and the plane except in the region shown in red and black in Figure 3 above. The plane is inclined at an angle of 0 = 16.5 degrees above horizontal. For the purposes of this problem, the acceleration of objects in freefall is g = 9.81 m/s?. The block begins at rest, leaning against a spring with a spring constant of k = 716 newtons per meter. At the start, the spring has a compressed length of x1 = 0.33 meters. The spring then expands to its equilibrium length of x2 = 0.63 meters, sending the block sliding up the ramp. The block has no friction with the plane except in the single region of length L = 0.8 meters, shown in red and black above. The coefficient of kinetic friction between the block and this region is uK = 0.24. The block slides past this region and continues up the plane. What is the speed of the block, in units of meters per second, when it has…

A cubical box (equal side lengths) of mass 1.7 kg (outline shown in blue in the figure) is supported at an angle = 16 degrees relative to a horizontal surface. The cable supporting the box is at an angle perpendicular to the in-plane diagonal of the box (shown as a dotted line). What is the minimum coefficient of static friction between the box and the horizontal surface such that the box will not slide? cable 0 + 45° Ө