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Question:

What is the point at which the lever pivots?

A The fulcrum

explanation

The fulcrum of a lever is the support point on which the lever pivots, like the center point of a see-saw. A lever is a simple machine, meaning that it amplifies an input force to provide a greater output force. The fulcrum's position affects the type of lever and the mechanical advantage provided by it.

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Which material is best suited for use as a boat anchor?

Metal

Foam and wood float and would therefore make poor boat anchors. Glass is not strong enough to be used as a boat anchor.

A farmer is attempting to pull a log with a line of rope attached to a tractor. Where should she watch for breakage on the rope?

Nearest to the tractor

The tension on the rope nearest to the tractor is the greatest. This is because tension is greatest where the force is being applied.

15 J of work were expended moving an 18 kg block. At what velocity did the block move?

1.3 m/s

To solve for velocity, you should use the formula W = KE, where Work = W, and Kinetic Energy = KE. This is because any work that is done to accelerate an object is converted to the kinetic energy of that object (the work-energy theorem). So, \(W= \frac{\mathrm{1} }{\mathrm{2} }m v^2 \). Plugging in the block's weight (18 kg) and the work done (15 J) will give you a velocity of 1.3 m/s.

What would happen to a balloon full of air if you moved it from above a water surface to ten feet below the water surface?

The volume of the balloon would decrease.

The volume of the balloon would decrease. The pressure of the water would press inward on the balloon and cause it to shrink in volume.

How is a wedge different from an inclined plane?

A wedge is used in motion

A wedge, unlike a slide, is useful in motion. For example, a knife slicing through a carrot.

A lever ____.

Multiplies force and changes direction

A lever both compounds force (makes it easier for you to lift something) and changes direction (when you push down on a lever, the object is lifted).

The center of gravity of a baseball bat would be best described as

near the fat end

The center of gravity is the place on an object where there is equal weight on either side.

What measures how much force is applied to an object in order to rotate it?

Torque

Torque is how much force is acting on a object, causing it to rotate. Think, for example, about a wrench turning a bolt.

A perfectly efficient machine ____.

Converts all the power applied to it into outputted force

A machine that is 100% efficient converts all of the power applied to it into output force. This is highly unlikely due to wear and tear, friction, and general imperfections.

Which of the following wedges generates the greatest amount of force.

11" long and 4" high

When a wedge is longer in relation to its height it decreases the amount of lift that occurs when the wedge moves through an object. This increases the amount of force generated.

What mechanical motion principle do the brakes in a car or on a bicycle use?

friction

When the brakes are applied, the brake pads rub on the wheel and the frictional force of this rubbing slows down the vehicle.