Mindblown: a blog about philosophy.
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Pivoted Rod with Unequal Masses
The figure shows a simple model of a seesaw. These consist of a plank/rod of mass mr and length 2x allowed to pivot freely about its center (or central axis), as shown in the diagram. A small sphere of mass m1 is attached to the left end of the rod, and a small sphere of mass m2 is attached to the…
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Net Torque on a Pulley
The figure below shows two blocks suspended by a cord over a pulley. The mass of block B is twice the mass of block A, while the mass of the pulley is equal to the mass of block A. The blocks are let free to move and the cord moves on the pulley without slipping…
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Linear and Rotational Quantities Conceptual Question
A merry-go-round is rotating at constant angular speed. Two children are riding the merry-go-round: Alan is riding at point A and Isamu is riding at point B. A) Which child moves with greater magnitude of velocity? => Isamu has the greater magnitude of velocity. B) Who moves with greater magnitude of angular velocity? => Both…
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Ladybugs on a Rotating Disk
Two ladybugs sit on a rotating disk, as shown in the figure (the ladybugs are at rest with respect to the surface of the disk and do not slip). Ladybug 1 is halfway between ladybug 2 and the axis of rotation. A) What is the angular speed of ladybug 1? => the same as the angular…
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Balancing Torques Ranking Task
A sign is to be hung from the end of a thin pole, and the pole supported by a single cable. Your design firm brainstorms the six scenarios shown below. In scenarios A, B, and D, the cable is attached halfway between the midpoint and end of the pole. In C, the cable is attached…
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Axis of Rotation and Moment of Inertia Ranking Task
Two identical uniform solid spheres are attached by a solid uniform thin rod, as shown in the figure. The rod lies on a line connecting the centers of mass of the two spheres. The axes A, B, C, and D are in the plane of the page (which also contains the centers of mass of…
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A Sculpture in Equilibrium
The abstract sculpture shown in the figure can be placed on a horizontal surface without tipping over. Different parts of the sculpture may be hollow or solid, or made of different materials, but the artist isn’t revealing any such information. A) Five locations labeled A through E are indicated on the diagram. Which of these,…
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Velocity of a Roller Coaster Ranking Task
Six roller-coaster carts pass over the same semicircular “bump.” The mass M of each cart (including passenger) and the normal force n of the track on the cart at the top of each bump are given in the figures. Rank the speeds of the different carts as each passes over the top of the bump. =>v2/R =…
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Understanding Newton’s Law of Universal Gravitation
Learning Goal: To understand Newton’s law of universal gravitation and be able to apply it in two-object situations and (collinear) three-object situations; to distinguish between the use of G and g. In the late 1600s, Isaac Newton proposed a rule to quantify the attractive force known as gravity between objects that have mass, such as those shown in…
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