# Homework Help: Help in Motion in Two Dimensions (Physics)

1. Oct 13, 2008

### Libos

I need help in seven exercises of physics, I just don't know what do... I'd like you to do one or more exercises with it's process so that I can analyze somehow the process and learn how do to it, I have an exam tomorrow and I have to study.. here are the problems:

1) An artillery shell is fired with an initial velocity of 300 m/s at 55.0° above the horizontal. To clear an avalanche, it explodes on a mountainside 42.0 seconds after firing. What are the x- and y- coordinates of the shell where it explodes, relative to its firing point? (I don't have any idea of that topic of coordinates, I don't know If I have to graph or something).

2) A placekicker must kick a Football from a point 36.0m (about 39 yd) from the goal, and the ball must clear the crossbar, which is 3.05 m high. When kicked, the ball leaves the ground with a velocity of 20.0m/s at an angle of 53° to the horizontal. (a) By how much does the ball clear or fall short of clearing the crossbar? (b) Does the ball approach the crossbar while still rising or while falling?

3) A fireman 50.0 m away from a burning building directs a stream of water from a ground-level fire hose at an angle of 30.0° above the horizontal. If the speed of the stream as it leaves the hose is 40.0 m/s, at what height will the stream of water strike the building?

4) A projectile is launched with an initial speed of 60.0 m/s at an angle of 30.0° above the horizontal. The projectile lands on a hillside 4.00 seconds later. Neglect air friction. (a) What is the projectile's velocity at the highest point of its trajectory? <Ans: 52.0 m/s horizontally> (b) What is the straight-line distance from where the projectile was launched to where it hits its target? <Ans: 212 m> (Answers where in the book but I need the process <3)

5) A soccer player kicks a rock horizontally off a 44.0-m-high cliff into a pool of water. If the player hears the sound of the splash 3.00 seconds later, what was the initial speed given to the rock? Assume the speed of sound in air to be 343 m/s.

6) A boy and a girl are tossing an apple back and forth between them. The apple is moving from left to right. Five points are marked on the path. Ignore air resistance. (a) At each of the five points draw an arrow that indicates that magnitude and direction of the apple's velocity when it passes through that point. (b) Make a second copy of the figure. This time, at each point, place an arrow indicating the magnitude and direction of any acceleration the apple exhibits at that point. <Here, I just need a brief explanation of what are those magnitudes and accelerations.)

7) A ball is thrown straight upward and returns to the thrower's hand after 3.00 seconds in the air. A second ball is thrown at an angle of 30.0° with the horizontal. At what speed must the second ball be thrown so that it reaches the same height as the one thrown vertically?

I repeat, from the first 5 questions, I need one or more so that I can use as a guide to solve the rest, because I have no I dea of what to do. And from the 2 last, I need the last one if you want because I don't know what to do. I'm sorry if I look like a retard asking so much, but I really need help :(

OR

Could you please give me the formulas to solve the given problems? Or make me know hwat's the data I need to find? Because I just don't have any idea of how to start in any of the problems :(

Thank you very much!

2. Oct 13, 2008

### LowlyPion

3. Oct 13, 2008

### Libos

Ok Thank you, I've achieved to do some problems, I'm missing number 5 and number 7 :/