91影视

Vector${\stackrel{鈫�}{V}}_1$is 6.6 units long and points along the negative X-axis. Vector${\stackrel{鈫�}{V}}_2$is 8.5 units long and points at$+{55}^o$to the positive X-axis. (a) what are the X and Y components of each vector? (b) Determine the sum${\stackrel{鈫�}{V}}_1+{\stackrel{鈫�}{V}}_2$(magnitude and angle).

If$\stackrel{\mathbf{鈫�}}{\mathbf{V}}\mathbf{=}{\stackrel{\mathbf{鈫�}}{\mathbf{V}}}_{\mathbf{1}}\mathbf{+}{\stackrel{\mathbf{鈫�}}{\mathbf{V}}}_{\mathbf{2}}$, is V necessarily greater than$V_1$and/or$V_2$? Discuss.

One ball is dropped vertically from a window. At the same instant, a second ball is thrown horizontally from the same window. Which ball has the greater speed at the ground level?

(a) The dropped ball

(b) The thrown ball

(c) Neither, as they both have the same speed on impact

(d) It depends on how hard the ball was thrown

William Tell must split the apple on top of his son鈥檚 head from a distance of 27 m. When William aims directly at the apple, the arrow is horizontal. At what angle should he aim the arrow to hit the apple if the arrow travels at a speed of 35 m/s?

Raindrops make an angle$胃$with the vertical when viewed through a moving train window (Fig. 3鈥�52). If the speed of the train is$v_T$, what is the speed of the raindrops in the reference frame of the Earth in which they are assumed to fall vertically?

A car moving at 95 km/h passes a 1.00-km-long train traveling in the same direction on a track that is parallel to the road. If the speed of the train is 75 km/h, how long does it take the car to pass the train, and how far will the car have travelled in this time? What are the results if the car and train are instead traveling in opposite directions?

A hunter aims directly at a target (on the same level) 38.0 m away. (a) If the arrow leaves the bow at a speed of 23.1 m/s, by how much will it miss the target? (b) At what angle should the bow be aimed so the target will be hit?

The cliff divers of Acapulco push off horizontally from rock platforms about 35 m above the water, but they must clear rocky outcrops at water level that extend out into the water 5.0 m from the base of the cliff directly under their launch point. See Fig. 3鈥�53. What minimum push-off speed is necessary to clear the rocks? How long are they in the air?

When Babe Ruth hit a homer over the 8.0-m-high right field fence 98 m from home plate, roughly what was the minimum speed of the ball when it left the bat? Assume the ball was hit 1.0 m above the ground and its path initially made a 36掳 angle with the ground.

At serve, a tennis player aims to hit the ball horizontally. What minimum speed is required for the ball to clear the 0.90-m-high net about 15.0 m from the server if the ball is 鈥渓aunched鈥� from a height of 2.50 m? Where will the ball land if it just clears the net (and will it be 鈥済ood鈥� in the sense that it lands within 7.0 m of the net)? How long will it be in the air? See Fig. 3鈥�54.