Two-dimensional Motion Part 4

Problem 3.22 A grasshopper leaps into the air from the edge of a vertical cliff, as shown in the figure below . Assume that , , and that . Part A Use the information given to find the initial speed of the grasshopper. Express your answer in meters per second to three significant figures. ANSWER: 1.43 Correct Part B Use the information given to find the height of the cliff. Express your answer in meters to three significant figures. ANSWER: 6.95 Correct Multiple Choice Question 3.1 Part A Shown here are the velocity and acceleration vectors for an object in several different types of motion. In which case is the object slowing down and turning to its right? ANSWER: Correct Multiple Choice Question 3.6 Part A A projectile is fired from the origin (at y = 0 m) as shown in the figure. The initial velocity components are = 950 and = 83 . The projectile reaches maximum height at point P, then it falls and strikes the ground at point Q. In the figure, the ycomponent of the acceleration of the shell at point P is closest to: ANSWER: -5 m/s2 zero -10 m/s2 +10 m/s2 +5 m/s2 Correct Prelecture Concept Question 3.12 Part A An object moves in a circular path at a constant speed. What is the relationship between the directions of the object's velocity and acceleration vectors? ANSWER: The velocity and acceleration vectors are perpendicular. The velocity vector points in a direction tangent to the circular path. The acceleration is zero. The velocity and acceleration vectors point in opposite directions. The velocity vector points toward the center of the circular path. The acceleration is zero. The velocity and acceleration vectors point in the same direction. Correct Prelecture Concept Question 3.06 Part A A football player kicks a football in a field goal attempt. When the football reaches its maximum height, what is the relationship between the direction of the velocity and acceleration vectors? Assume air resistance is negligible. ANSWER: At the maximum height, the velocity and acceleration vectors point in opposite directions. At the maximum height, both the velocity and acceleration vectors are zero. At the maximum height, the velocity and acceleration vectors are parallel to each other. At the maximum height, the velocity and acceleration vectors are perpendicular to each other. Correct Prelecture Concept Question 3.05 Part A A player kicks a soccer ball in a high arc toward the opponent's goal. When the soccer ball reaches its maximum height, how does its speed at this point compare to its initial speed? Assume air resistance is negligible. ANSWER: The speed at its highest point is equal to its initial speed. The speed at its highest point is zero. The speed at its highest point is greater than its initial speed. The speed at its highest point is less than its initial speed. The speed at its highest point cannot be determined unless the angle at which the soccer ball is kicked is known. Correct Multiple Choice Problem 3.13 An object traveling at speed V/2 in a circle of radius 2R has an acceleration a. Part A If both speed and radius are doubled, the new acceleration will be ANSWER: a/2. 2a. a. a/4. Correct Multiple Choice Question 3.10 Part A A projectile is fired at time t = 0.0 , from point 0 at the edge of a cliff, with initial velocity components of = 60 and = 500 . The projectile rises, then falls into the sea at point P. The time of flight of the projectile is 125 . In the figure, the x-coordinate of the projectile when its y-component of velocity equals 400 upward is closest to: ANSWER: 640 m 580 m 550 m 520 m 610 m Correct Speed of a Softball A softball is hit over a third baseman's head with some speed at an angle above the horizontal. Immediately after the ball is hit, the third baseman turns around and begins to run at a constant velocity . He catches the ball later at the same height at which it left the bat. The third baseman was originally standing from the location at which the ball was hit. Part A Find . Use for the magnitude of the acceleration due to gravity. Express the initial speed numerically in units of meters per second to three significant figures. You did not open hints for this part. ANSWER: = Part B Find the angle in degrees. Express your answer numerically in degrees to three significant figures. You did not open hints for this part. ANSWER: = Score Summary: Your score on this assignment is 97.4%. You received 360.56 out of a possible total of 370 points, plus 0 points of extra credit.