I. HW # 3: Intro to equations of motion. Here are 3 basic ...



Cliff Diving and MoreHere is some more practice for you in using the equations of motion. For freefall problems use g = 9.8 m/s2. Remember to follow these steps:Draw a sketch: Show the object of interest at the beginning and end of the interval. Assign a + direction with a + black arrow. Attach and label all the relevant parameters (color code ‘em): Δx, vo, vf, a and Δt.If the acceleration is constant, identify the missing variable and select the equation of motion that goes with it. If the acceleration is not constant, abort the mission!Solve the equation algebraically first.Finally, plug in the numbers, round to the correct number of sig figs, and check the units.You decide to try cliff diving while on vacation in Hawaii. (Bad decision.) You step off a cliff that is 30.5 m high. How fast are you going when you hit the water? Remember that you know what the acceleration due to gravity is. You also know what vo is…As a private detective, you are called in to investigate an accident. A car was traveling at an unknown velocity when the driver slams on the brakes, losing speed at a constant rate of 8.0 m/s every second. The car slams into a truck after skidding for a time of 3.0 seconds. The skid marks are 55 m long. What was the velocity of the car when it began to skid? (Find vo.)How fast was the car moving the instant before it plowed into the truck? (Find vf.)You are spelunking with a friend when your flashlight dies. You feel along the cave floor until you come to a chasm of unknown depth. After blubbering for a while in self-pity, you remember that you know PHYSICS. You tell your friend to feel around for a pebble, drop it into the chasm and listen for it to hit bottom. “We can estimate the depth of the chasm by timing the fall,” you gush. Your friend releases the pebble and you estimate its time of fall to be about 0.50 seconds. How deep is the chasm? (Which variable should you find?)Is this a safe distance to fall? How fast would you be going immediately before you hit bottom? (Which variable should you find? New sketch required.)Turns out that your “friend” doesn’t like you very much. Instead of just dropping the pebble (which would have meant vo is 0) she secretly hurls the stone downward with an initial velocity of 20 m/s. How deep is the chasm actually? (Assume that the time of fall is still 0.50 seconds. New sketch required.) ................
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