Question

Projectile Motion Instructions 1. Draw the schematic of the situation described in the wording of the problem. This schematic includes a list of the data given in the wording of the problem, such as initial position ( yo), initial velocity vo V V , final position (XY), final velocity (v, V, ) or maximum heightlynas) Make a decision on whether you want to use "y" or "h" for the vertical axis and keep it consistent throughout all the problems. Write down the units. 2. If you are given ve instead of thex and y components of the velocity, decompose that velocity into its x and y components before anything. If the problem does not give you the value of the angle the initial velocity forms with the horizontal direction (), leave the components of the initial velocity as a function of the angle. E.g. =5" , = 5 case":v, = 5 sine" 3. you make an assumption for the data that is not explicitly in the wording of the problem, write down that it is an assumption, and write down a short reasoning for that assumption. Double check to make sure your assumption is not unwarranted. 4. Correctly doing points 1 through 3 is 25% of each problem's score. 5. Write down the equations of motion for the x-axis. Remember that in the x-axis there is no acceleration, so it's the equations of motion for constant velocity: X = Xo+vt;V = Vxo = constant Try to solve this equation by inserting the values from the data. Write down the units. You will always have at least one unknown value in this equation, and more than likely, you will have two unknown values. Correctly doing this will give you 15% of a problem's score. 6. Write down the equations of motion for the y-axis. Remember that motion in the yaxis is a free fall, so it's the equations for 1D accelerated motion with as-g: y = y + 3yott wy = yogt u-v= -2g(y-yo) Often, none of these equations can be solved by themselves. Compare them with the equation for the x-axis. Chose the y-axis equation that, when put together with the x-axis equation, gives you a system of 2 equations with 2 unknown values. Then substitute the known data in the yaxis equation you have chosen. Finding the correct yaxis equation for this system of equations gives you 35% of a problem's score. 7. Solve correctly the system of equations, and the rest of necessary steps to arrive at the solution the problem asks. Writing down every step, the solution, and all the units in every step, give the remaining 25% of the problem's score. 8. There is no need to switch to IS Units. Feet and cm are acceptable units for the result. Just be careful when the wording of the problems gives different units for the same type of magnitude.

Problem 3:

In an ordinary television set, the electron beam consists of electrons shot horizontally at the television screen with a speed of about 5 x 107 m/s. How far does a typical electron fall as it moves the approximately 40 cm from the electron gun to the screen? For comparison, how far would a droplet of water shot horizontally at 2 m/s from a hose drop as it moves a horizontal distance of 40 cm?

Answer 1

Given that Speed: 51 mls diuytamce = 4O Cm h8ittal sped 2mls drom heritordaly time t t lo.40)m 8161 sec fon wtatally Jayoyt + ae 2 y=(0) (8167 see)+ (8)8k 16 31l616m der a droplet : 0.10n o.20 sec y Voyt + at 2 (0)(0.20) + (9.8)(0.20) 12 yao.196m