Elasticity (Lecture 2 and 3)

Question 1

What is Hookes Law?

Answer 1

The law states that if a tensile (stretching) force F is applied to a spring with a spring constant k, the
extension ∆L of the spring is given by: Force/Spring Constant

Question 2

What is the equation of Hookes Law?

Answer 2

Change in Length=Force/Springs Constant
L=F/k

Question 3

What is the Si unit of k?

Answer 3

N m^-1

Question 4

What does a spring with a high value of K indicate?

Answer 4

It is very stiff (very hard to strech)

Question 5

In a Hookes Law graph what is the y axis and x axis?

Answer 5

y axis is force
X axis is extension

Question 6

What does the straight line in a hookes law graph represent?

Answer 6

It represents the springs constant

Question 7

What is the straight line region called?

Answer 7

Elastic

Question 8

What does Yield Point mean?

Answer 8

The point at which the material starts to deform plastically

Question 9

What is the curved region of the graph called?

Answer 9

Plastic

Question 10

For 2 springs connected in series what is the springs constant equation?

Answer 10

K total= K (1) x K (2)/ K (1) + K (2)

Question 11

What happens if 2 springs have the same springs constant that are connected in series?

Answer 11

K total= K/2

Question 12

What is the springs constant if 2 springs are connected in parallel?

Answer 12

K total= K (1) + K (2)

Question 13

What is the equation if 2 springs connected in parallel have the same springs constant

Answer 13

K total=2k

Question 14

What is stress equation and its unit?

Answer 14

Force/Area
Pa

Question 15

What is strain equations and its unit?

Answer 15

Change in Length/Length
No unit

Question 16

What is Young Modulus equation and its unit?

Answer 16

Stress/Strain
MPa or GPa

Question 17

Other expressions for Young Modulus?

Answer 17

Young Modulus= (F/A)/(L/L)
E=FL/(Axchange in L)
Change in L=FL/AE

Question 18

What is Normal Stress

Answer 18

Force which acts normal to the surface area that acts 90 degrees to the contact area.

Question 19

What is Sheer Force?

Answer 19

When a force acts parallel to the surface area it is called a shear force.

Question 20

What is a sheer stress?

Answer 20

Thus shear stress is the ratio of shear force to the surface area.
Shear strain is the (small) angle between the undeformed and deformed object after applying the shear
force.
Shear modulus G is the ratio of shear stress to shear strain.

Question 21

What is Bulk Stress?

Answer 21

In bulk stress, the force is applied to a body equally in all directions and perpendicular to the surface.
Bulk stress is the ratio of such a force to the surface area.
Bulk strain is the ratio of change of volume to the original volume.
Bulk modulus B is the ratio of bulk stress to bulk strain.

Question 22

What is Ultimate Tensile Stress

Answer 22

Maximum stress that an object can support in theory.

Question 23

What is the equation of applied stress?

Answer 23

Ultimate Tensile Strength/Safety Factor

Question 24

What is the value of M?

Answer 24

10^6

Question 25

What is the value of G?

Answer 25

10^9

Question 26

What is bending?

Answer 26

When a force is applied and the edges remain curved