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Chapter 4: Q25P (page 85)
The current world-record motorcycle jump is , set by Jason Renie. Assume that he left the take-off ramp at to the horizontal and that the take-off and landing heights are the same. Neglecting air drag, determine his take-off speed.
The take-off speed of the Jason Renie鈥� is
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Curtain of death.A large metallic asteroid strikes Earth and quickly digs a crater into the rocky material below ground level by launching rocks upward and outward. The following table gives five pairs of launch speeds and angles (from the horizontal) for such rocks, based on a model of crater formation. (Other rocks, with intermediate speeds and angles, are also launched.) Suppose that you are at x=20 kmwhen the asteroid strikes the ground at time t=0nd position x=0(Fig. 4-52). (a) At t=20 s, what are the xand y coordinates of the rocks headed in your direction from launches A through E? (b) Plot these coordinates and then sketch a curve through the points to include rocks with intermediate launch speeds and angles.The curve should indicate what you would see as you look up into the approaching rocks.
A suspicious-looking man runs as fast as he can along a moving sidewalk from one end to the other, taking . Then security agents appear, and the man runs as fast as he can back along the sidewalk to his starting point, taking . What is the ratio of the man鈥檚 running speed to the sidewalk鈥檚 speed?
A plane flies east from city A to city B inand thensouth from city B to city C in. For the total trip, what are the (a)magnitude and(b)direction of the plane鈥檚 displacement, the(c)magnitude and(d)direction of the average velocity, and(e)it鈥檚 average speed?
A woman who can row a boat at 6.4 km/hin still water faces a long, straight river with a width of 6.4 km and a current of 3.2 km/h. Letpoint directly across the river andpoint directly downstream. If she rows in a straight line to a point directly opposite her starting position, (a) at what angle tomust she point the boat and (b) how long will she take? (c) How long will she take if, instead, she rowsdownthe river and then back to her starting point? (d) How long if she rows 3.2 kmupthe river and then back to her starting point? (e) At what angle toshould she point the boat if she wants to cross the river in the shortest possible time? (f) How long is that shortest time?
In basketball, hang is an illusion in which a player seems to weaken the gravitational acceleration while in mid-air. The illusion depends much on a skilled player鈥檚 ability to rapidly shift the ball between hands during the flight, but it might also be supported by the longer horizontal distance the player travels in the upper part of the jump than in the lower part. If a player jumps with an initial speed ofat an angle of , what percent of the jump鈥檚 range does the player spend in the upper half of the jump (between maximum height and half maximum height)?
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