At 20 ◦C, a rod is exactly 20.05 cm long on a steel ruler. Both the rod and the ruler are placed in an oven at 270 ◦C, where the rod now measures 20.11 cm on the same ruler. What is the coefficient of linear expansion for the material of which the rod is made? Take αsteel = 1.2 × 10−5 K−1 .

The coefficient of expansion is

∝=1.56*10^-5/C

Explanation:

The problem is based on linear expansivity

The linear expansivity of a solid is the fractional increase in length per unit degree rise in temperature.

It is given as

∝=ΔL/ΔT

Given L1=20.5cm to m =20.5/100

=0.205m

L2=20.11cm to m= 20.11/100

= 0.2011nlm

T1=20°c

T2=270°c

∝=0.2011-0.205/270-20

∝=0.0039/250

∝=0.0000156

∝=1.56*10^-5/C

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg