Physics Ch 9 MC

The figure shows an overhead view of a large door that is free to pivot on a hinge along its left edge. A force is applied to the door in four different ways. The magnitude of the force is the same in each case. In which case is the torque on the door the largest? a. hinge Force(upward, straight, at the other end) b. hinge Force (upward, diagonal, at the other end) c. hinge Force (upward, straight, middle) d. hinge Force (sideways towards the hinge)

A

The drawing shows two objects rotating about a vertical axis. The mass of each object is given in terms of m0, and its perpendicular distance from the axis is given in terms of r0. Which of the following is true? (A= r0, 10m0; B= 2r0, 2m0) a. Object A has a greater moment of inertia than Object B. b. Object B has a greater moment of inertia than Object A. c. The moments of inertia of Objects A and B are equal.

a. Object A has a greater moment of inertia than Object B.

A cloud of interstellar gas is rotating. Because the gravitational force pulls the gas particles together, the cloud shrinks, and, under the right conditions, a star may be formed. Would the angular velocity of the star be less than, greater than, or equal to the angular velocity of the rotating gas? a. Equal to b. Greater than c. Less than

b. greater than

What is the point at which the weight of rigid object can be considered to act when producing a torque on the object? a. The center of force. b. The center of gravity. c. The center of torque. d. The center of inertia

b. the center of gravity

Which of the following is true about a rigid body in dynamic equilibrium? a. The body cannot have translational or rotational motion of any kind. b. The body can have translational motion, but it cannot have rotational motion. c. The body can have translational motion and rotational motion, as long as its translational and angular accelerations are equal to zero. d. The body cannot have translational motion, but it can have rotational motion.

c. The body can have translational motion and rotational motion, as long as its translational and angular accelerations are equal to zero.

A hoop of mass M and radius R and a solid cylinder of mass M and radius R are rolling along level ground with the same translational speed. Which object has the greater total kinetic energy? a. The solid cylinder b. Both have the same total kinetic energy c. The hoop

c. the hoop

A hoop, a solid cylinder, a spherical shell, and a solid sphere are placed at rest at the top of an inclined plane. All the objects have the same radius. They are all released at the same time and allowed to roll down the plane. Which object reaches the bottom first? a. The spherical shell b. The solid cylinder c. The solid sphere d. The hoop

c. the solid sphere

A woman is sitting on a spinning piano stool with her arms folded. Ignore any friction in the spinning stool. When she extends her arms outward, which of the following is true? a. Her angular speed increases, and her angular momentum decreases. b. Her angular speed decreases, and her angular momentum increases. c. Her angular speed increases, and her angular momentum remains constant. d. Her angular speed decreases, and her angular momentum remains constant.

d. Her angular speed decreases, and her angular momentum remains constant.

Two forces are applied to a ship's wheel. The wheel is not rotating. Which of the following must be true? a. F1 must be equal to F2. b. The magnitude of the torque created by F1 must be greater than the magnitude of the torque created by F2. c. The magnitude of the torque created by F2 must be greater than the magnitude of the torque created by F1. d. The magnitude of the torque created by F1 must be equal in magnitude to the torque created by F2.

d. The magnitude of the torque created by F1 must be equal in magnitude to the torque created by F2.

A uniform ladder is at rest leaning against a smooth wall (frictionless) as shown in the figure at the left. The base of the ladder is on rough ground (friction). The corresponding free-body diagram for the ladder is shown in the figure at the right. Which of the following must be true? a. The sum of the forces in the x-direction must be equal to zero. b. The sum of the forces in the y-direction must be equal to zero. c. The sum of the torques acting on the ladder must be equal to zero. d. All of the above must be true.

d. all of the above must be true

The same force F is applied to the edge of two hoops as the drawing below shows. The hoops have the same mass, whereas the radius of the larger hoop is twice the radius of the smaller one. The entire mass of each hoop is concentrated at its rim, so the moment of inertia is equal toMr^2 , where M is the mass of the hoop, and is the radius. Which hoop has the greater angular acceleration, and how many times as great is it compared to the other hoop? a. The larger hoop; two times as great. b. The smaller hoop; four times as great. c. The larger hoop; four times as great. d. The smaller hoop; two times as great.

d. the smaller hoop; two times as great

Which of the letters below most closely matches the location of the center of gravity of the baseball bat? (picture of bat with point A at the small end, point B in the thin section after point A, point C the thicker section on the middle, point D on the thick end)

point C