Zipline casters are steel wheels that roll along a steel cable. Data Blocks: Materials Drag Coefficient Shape Steel on steel 0.74 0.57 Aluminum on steel 0.61 0.47 Sphere 0.47 Copper on steel Rubber on concrete (dry) Rubber on concrete (wet) Wood on wood Glass on glass Teflon on Teflon Teflon on steel 0.53 0.36 1.0 0.8 Half-sphere- 0.42 0.3 0.25 0.25-0.5 0.2 0.94 0.4 Cone 0.50 0.04 0.04 0.04 0.04 Cube Waxed wood on wet snow Waxed wood on dry snow Metal on metal (lubricated) Ice on ice 1.05 0.14 0.1 0.10 0.04 Angled Cube 0.15 0.06 0.80 0.1 0.03 Synovial joints in humans Very rough surfaces 0.01 0.003 Long Cylinder 0.82 1.5 Short Cylinder 1.15 Table 1: Reference values for the rolling resistance coefficient (f;) Conditions Rolling resistance coefficient (fr) Streamlined 0.04 Body Car tire on smooth tamac road 0.01 Car tire on concrete road 0.011 Streamlined 0.09 Half-body Car tire on a rolled gravel road 0.02 Tar macadam road 0.025 Measured Drag Coefficients Unpaved road 0.05 Bad earth tracks 0.16 Loose sand 0.15-0.3 Truck tire on concrete or asphalt road 0.006-0.01 Wheel on iron rail 0.001-0.002 oマロ令 3. From the platform landing, you travel along a rugged trail to a river. The guide tells you that the river at this point is well behaved, with a velocity of about 16 m/s. While you are loading into a white-water raft, you do some estimation and assess the boat plus load to have a mass of 850 kg. As you begin drifting down the river, you begin counting, finding that it takes about 12 seconds until you are moving at the same pace as the river. You drift along the river for 20 more minutes. You see a landing at the top of a waterfall. You paddle your boat to a stop over the next 3 minutes to reach the pier. Take all the motion as 'uniform' and to the left relative to the viewer. а. Draw your free body diagram the moment after you leave the loading dock. Clearly indicate net force. b. What is the initial force being exerted by the river? с. Draw your free body diagram the moment after you begin to paddle. Clearly indicate the net force. d. With what force will you need to paddle to stop at the pier?