quiz2-solutions

# The sum of the two components of acceleration is best

This preview shows pages 2–5. Sign up to view the full content.

points down in the picture. The sum of the two components of acceleration is best represented by a vector pointing left an down, that is (e): ~a c ~a t 2

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2. For this problem neglect air resistance. Find the best way to complete the sentence: The acceleration of a baseball that has been batted from home toward center field ... (a) remains constant throughout the trajectory. 4 (b) is largest when the ball reaches its highest point along its trajectory. (c) is smallest when the ball reaches its highest point along its trajectory. (d) is tangential to the path of the ball. (e) vanishes instantaneously when the ball reaches its highest point along its trajectory. ANS: This is projectile motion. The acceleration is constant, of magnitude g , points down (answer (a) is correct). (b), (c) and (e) are incorrect because the acceleration is constant, while (d) has the wrong direction (its the velocity that is tangential to the path). 3. Jet streams flow from west to east in the upper portion of the troposphere. You want to pilot a jet-plane from Las Vegas, NV, directly north to Boise, ID, and you know that most of the time you will be flying through the troposphere. In order to complete your trip by a straight line flight you should aim your plane, roughly (a) west of north 4 (b) east of north (c) north (d) west of south (e) east of south ANS: Addition of velocities. Let ~v JG = velocity of Jet stream relative to Ground, ~v PG = velocity of plane relative to Ground and ~v PJ = velocity of plane relative to Jet stream. Then ~v PG = ~v PJ + ~v JG . Graphically ~v PJ ~v JG ~v PG W E S N 3
4. Two identical balls are thrown from ground level at an angle of 30 above the ground. Ball A is thrown with twice the initial velocity as ball B. If it takes 4 s for ball B to hit the ground, the time t A it takes ball A to hit the ground is (neglecting air resistance) (a) 8 s 4 (b) 4 s (c) 2 s (d) 1 s (e) 16 s ANS: Projectile motion. Consider x (horizontal) and y (vertical) components of motion separately. For vertical displacement we have y ( t ) = - 1 2 gt 2 + v 0 y t + y 0 . Stating at t = 0 from y (0) = y 0 , the condition that the ball hits the ground at some later time t g is y ( t g ) = y 0 .

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern