answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
IgorLugansk [536]
2 years ago
7

Roads often have to be repaved because they crack over time. Sometimes this cracking is due to the fact that the roads (as well

as other objects) have a tendency to expand when heated and contract when cooled. Thermal expansion and contraction are examples of
A.
physical and chemical changes.
B.
physical changes.
C.
chemical changes.
D.
neither physical nor chemical changes.
Physics
1 answer:
Finger [1]2 years ago
4 0
B. Physical Change - T<span>he molecules do not change shape or size. They do not contract or expand only.</span>
You might be interested in
Suzette had prepared the graph below to add to her lab
Charra [1.4K]

Answer:

A title

Explanation:

Because this is middle school.

4 0
2 years ago
Read 2 more answers
The gravity tractor is a proposed spacecraft that will fly close to an asteroid whose trajectory threatens to impact the Earth.
Talja [164]

Answer:

F_g=461lb_f

Explanation:

First calculate the mass of the asteroid. To do so, you need to find the volume and know the density of iron.

If r = d/2 = 645ft, then:

V = \frac{4}{3} \pi r^3

V = 1.124*10^{9}ft^3

So

\delta_{iron}=m/V=491lb/ft^3

m=V*\delta=5.519*10^{11}lb

Once you  know both masses, you can calculate the force using Newton's universal law of gravitation:

F_g=G\frac{m_1m_2}{d^2}

Where G is the gravitational constant:

G= 1.068846 * 10^{-9} ft^3 lb^{-1} s^{-2}

F_g=461lb_f

4 0
2 years ago
A river flows with a uniform velocity vr. A person in a motorboat travels 1.22 km upstream, at which time she passes a log float
storchak [24]

Answer:

 t ’= \frac{1450}{0.6499 + 2 v_r},  v_r = 1 m/s       t ’= 547.19 s

Explanation:

This is a relative velocity exercise in a dimesion, since the river and the boat are going in the same direction.

By the time the boat goes up the river

        v_b - v_r = d / t

By the time the boat goes down the river

        v_b + v_r = d '/ t'

let's subtract the equations

       2 v_r = d ’/ t’ - d / t

       d ’/ t’ = 2v_r + d / t

       t' = \frac{d'}{ \frac{d}{t}+ 2 v_r }

In the exercise they tell us

         d = 1.22 +1.45 = 2.67 km= 2.67 10³ m

         d ’= 1.45 km= 1.45 1.³ m

at time t = 69.1 min (60 s / 1min) = 4146 s

the speed of river is v_r

      t ’= \frac{1.45 \ 10^3}{ \frac{ 2670}{4146} \  + 2 \ v_r}

      t ’= \frac{1450}{0.6499 + 2 v_r}

In order to complete the calculation, we must assume a river speed

          v_r = 1 m / s

       

let's calculate

      t ’= \frac{ 1450}{ 0.6499 + 2 \ 1}

      t ’= 547.19 s

8 0
2 years ago
Corey, whose mass is 95 kg, stands on a bathroom scale in an elevator. The scale reads 850 N for the first 3.0 s after the eleva
lyudmila [28]

Answer:

v₂ = 2.568 m/s

Explanation:

given,

mass of Corey = 95 Kg

reading of sale for first 3 s when elevator start to move = 850 N

scale reading for the next 3.0 s = 930 N

Gravitation force acting =

  F = m g

  F = 95 x 9.8

  F = 931 N

using newtons second law, due to movement of elevator

    F_{net} = m a

 W - N = m a₁

931- 850 = 95 x a₁

    a₁ = 0.852 m/s²

now,

velocity calculation

v₁ = a₁t

v₁ = 0.852 x 3 = 2.557 m/s

now, For second case

931 - 930 = 95 x a₂

a₂ = 0.011 m/s²

now, velocity after 4 s

v₂ = v₁ + a₂ t

v₂ = 2.557+ 0.011 x (4 - 3)

(4-3) because velocity after 3 second is calculate we need to calculate velocity after 4 s from beginning.

v₂ = 2.557 + 0.011

v₂ = 2.568 m/s

velocity of the elevator is equal to v₂ = 2.568 m/s

7 0
2 years ago
A force Fof 40000 lbf is applied to rod AC the negative Y-direction. The rod is 1000 inches tall. A Force P of 25 lbf is applied
erastova [34]

Answer:

The answer is "effective stress at point B is 7382 ksi "

Explanation:

Calculating the value of Compressive Axial Stress:

\to \sigma y  =\frac{F}{A} = \frac{4 F}{( p d ^2 )} = \frac{(4 x ( - 40000 \ lbf))}{[ p \times (1 \ in)^2 ]} = - 50.9 \ ksi \\

Calculating Shear Transverse:

\to \frac{4v}{ 3 A} = \frac{4 (75 \ lbf + 25 \ lbf)}{ \frac{3 ( lni)^2}{4}}

        = \frac{4 (100 \ lbf)}{ \frac{3 ( lni)^2}{4}} \\\\ = \frac{400 \ lbf)}{ \frac{3 ( lni)^2}{4}} \\\\= 0.17 \ ksi

= R \times 200 \ in - P \times 100 \ in = 12500 \ lbf \times\  in

\to \sigma' =[ s y^2 +3( t \times y^2 + t yz^2 )] \times \frac{1}{2}\\\\

       = [ (-50.9)^2 +3((63.7)^2 +(0.17)^2 )] \times \frac{1}{2}\\\\=[2590.81+ 3(4057.69)+0.0289]\times \frac{1}{2}\\\\=[2590.81+12,173.07+0.0289] \times \frac{1}{2}\\\\=14763.9089\times \frac{1}{2}\\\\ = 7381.95445 \ ksi\\\\ = 7382 \ ksi

8 0
2 years ago
Other questions:
  • Scientists in a test lab are testing the hardness of a surface before constructing a building. Calculations indicate that the en
    15·1 answer
  • In at least 150 words, discuss how Chang's use of personification, metaphor, or connotation express one his themes in "Garden of
    8·1 answer
  • Analyze at the image below and answer the question that follows.
    14·2 answers
  • An optical disk drive in your computer can spin a disk up to 10,000 rpm (about 1045 rad / s). if a particular disk is spun at 79
    9·1 answer
  • Two rockets are flying in the same direction and are side by side at the instant their retrorockets fire. Rocket A has an initia
    8·1 answer
  • Titin is a spring-shaped elastic protein that attaches to the thick filament and anchors it to the Z-discs of a sarcomere. If ti
    15·1 answer
  • An experiment to measure the speed of light uses an apparatus similar to Fizeau's. The distance between the light source and the
    9·1 answer
  • Is the statement "An object always moves in the direction of the net force acting on it" true or false
    10·1 answer
  • Which economic idea did Adam Smith promote in The Wealth of Nations?
    9·2 answers
  • Examine each of the four circles containing molecules.
    6·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!