Elasticity and Hookes Law - ppt

Elasticity and hookes law

Elasticity

In physics, elasticity- property by which an object that changes in shape and size under the action of an applied force and recovers its original shape when the force is removed

4 Examples of elasticity

elongation ("stretching")

Compression ("squeezing")

Flexion ("Bending")

Torsion ("Twisting")

Elongation ("stretching") - a classic in clothing. It could also be 2-dimensional like jumping. example is a rubber band, or a spring that pulls, or the "elastic" bands surface of a trampoline.

Compression ("squeezing") - a spring that pushes like the coil springs under a vehicle, or a ball which temporarily flattens when hit by a bat or golf club. Another example is when you pinch the skin on the back of your hand, let go, and watch the skin pull itself back into place.

Flexion ("Bending") - a diving board, leaf springs under a vehicle, a bow being used to shoot an arrow.

Hooke's law is named after the 17th century British physicist Robert Hooke. He first stated this law in 1660 as a Latin anagram, whose solution he published in 1678 as Ut tensio, sic vis, meaning, "As the extension, so the force".

Torsion ("Twisting") - one type of spring used under a vehicle is the "torsion bar", so when the car hits a bump it twists a steel bar which untwists after the bump, absorbing the energy and smoothing the ride.

Hookes law

Hooke's law

Robert Hooke- an English physicist showed though an experiment that with in its elastic limit the deformation of an elastic body is directly proportional to the applied force

In mechanics, and physics, Hooke's law of elasticity is an approximation that states that the extension of a spring is in direct proportion with the load applied to it. Many materials obey this law as long as the load does not exceed the material's elastic limit. Materials for which Hooke's law is a useful approximation are known as linear-elastic or "Hookean" materials. Hooke's law in simple terms says that strain is directly proportional to stress.

Formula:

where:x is the displacement of the end of the spring from its equilibrium position (in SI units: "m");F is the restoring force exerted by the material (in SI units: "N" or kgms-2); andk is a constant called the rate or spring constant (in SI units: "N·m-1" or "kgs-2").

Formula states:

When this holds, the behavior is said to be linear. If shown on a graph, the line should show a direct variation. There is a negative sign on the right hand side of the equation because the restoring force always acts in the opposite direction of the displacement (for example, when a spring is stretched to the left, it pulls back to the right).

QUIZ

QUIZ

1-4- give the 4 examples of elasticity?5- an English physicist showed though an experiment that with in its elastic limit the deformation of an elastic body is directly proportional to the applied force6-7- what is elasticity?TRUE or FALSE8- Ut tensio, sic vis, meaning, "As the extension, so the force".9- Hooke's law is named after the 17th century British physicist Robert Hooke.10- x is a constant called the rate or spring constant

answers

1-4 elongation, compression flexion, torsion5- Robert Hooke6-7- elasticity- property by which an object that changes in shape and size under the action of an applied force and recovers its original shape when the force is removedTRUE OR FALSE8- true9- true10- false