You throw a pebble upward with a velocity V, at an angle theta, from a roof 6 m above the ground. If the pebble rises upward to a height of 6 m above the roof, then falls to the ground below, its speed when it hits the ground is: 1. Exactly Vo 2. Between Vo and v2vo 3. Exactly V2vo 4. Greater than v2vo 5. Not enough information to determineIn the figure, a block weighing 22.0 N is held at rest against a vertical wall by a horizontal force F of magnitude 61 N. The coefficient of static friction between the wall and the block is 0.55, and the coefficient of kinetic friction between them is 0.38. In six experiments, a second force P is applied to the block and directed parallel to the wall with these magnitudes and directions: (a)34 N, up, (b)11 N, up, (c)48 N, up, (d)62 N, up, (e)9.3 N, down, and (f)18 N, down. In each experiment, what is the frictional force on the block, including sign? Take the direction up the wall as positive, and down the wall as negative. Next, calculate the acceleration, including sign, of the block in each case. Note that acceleration is zero if the block does not move. (g) What is the acceleration in (a)? (h) What is the acceleration in (b)? (i) What is the acceleration in (c)? (j) What is the acceleration in (d)? (k) What is the acceleration in (e)? (1) What is the acceleration in (f)?Continuation of Problem 8 and Problem 37. Another explanation for the sliding stones of Racetrack Playa in Death Valley, California is that the stones move only when the water dumped on the playa during a storm freezes into a large, thin sheet of ice. The stones are trapped in place in the ice. Then, as air flows across the ice during a wind, the air-drag forces on the ice and stones move them both, with the stones gouging out the trails. The magnitude of the air-drag force on this horizontal "ice sail" is given by Dice = 4CicePAiceVz, where Cice is the drag coefficient (2.0 * 10"), p is the air density (1.21 kg/m ), Aice is the horizontal area of the ice, and vis the wind speed along the ice. Assume the following: The ice sheet measures 280 m by 430 m by 3.3 mm and has a coefficient of kinetic friction of 0.13 with the ground and a density of 917 kg/m. Also assume that 100 stones of mass 19 kg are trapped in the ice. To maintain the motion of the sheet, what is the required wind speed near the sheet