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2 years ago

A car is travelling at a speed of 30m/s on a straight road. what would be the speed of the car in km

Physics

2 answers:

mart [117]2 years ago

7 0

Answer:

$= \frac{30 \times {10}^{ - 3} }{1} \\ = 0.03 \: km \: per \: second$

katrin [286]2 years ago

3 0

Answer:

108 km/hr or 0.03 km/s

Explanation:

conversion factor for m/s to km/hr is 5/18

conversion factor for m/s to km/s is 1/1000

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The increase in volume of matter that occurs when matter is heated. a) Contraction b) Expansion c) kinetic energy d) Volume

katrin2010 [14]

Answer:

b) Expansion

Explanation:

In science, matter can be defined as anything that has mass and occupies space. Any physical object that is found on earth is typically composed of matter. Matter are known to be made up of atoms and as a result has the property of existing in states.

Generally, matter exists in three (3) distinct or classical phases and these are; solid, liquid and gas.

A physical change can be defined as a type of change that involves an increase or decrease in the volume of a physical object (object). Also, this change can be reversed to the original state under certain conditions.

The increase in volume of matter that occurs when matter is heated causes an expansion.

This ultimately implies that, when a physical object (matter) is heated for a specific period of time, it result in an increase in the volume of the object; this phenomenon is generally referred to as expansion.

On the other hand, a decrease in volume of a physical object (matter) as a result of heat is known as contraction.

7 0

2 years ago

Which of the following statements about comets is true? A. Comets rarely fall into an orbit around the Sun. They usually enter t

GREYUIT [131]

<h2>Right answer: Comets have very elliptical orbits that usually take them far beyond the orbit of Pluto, but also take them closer to the Sun than Earth</h2>

Comets are celestial bodies constituted by ice, dust and rocks that orbit around the Sun, after having been altered by the Oort cloud; following different trajectories that can be <u>highly eccentric elliptical</u><u> </u>(periodic trajectories), parabolic or hyperbolic.

One of the main characteristics of a comet is that it travels quite fast, on its way around the Sun and has a long tail. It should be noted that the tails of comets always go in the opposite direction to the Sun (due to the radiation pressure of sunlight).

Therefore, the correct option is C.

4 0

3 years ago

Read 2 more answers

Imagine an alternate universe where the value of the Planck constant is . In that universe, which of the following objects would

HACTEHA [7]

Question: The planck constant was not given. In this calculation, planck constant of 6.62607*10^-9 Js is used for the calculation.

Answer:

(a) A virus -------------Classical

(b) A buckyball -----Classical

(d) A turtle ------------Quantum

Explanation:

Calculating the wavelength using the formula;

λ= h/(mv)

where

λ= Wavelength

h = Planck Constant = 6.62607*10^-9 Js

m = mass in kg

v = velocity in m/s

Virus size = 280. nm = 2.80*10⁻⁷ m

A Virus:

m = 9.4 x 10-17 g 9.4*10⁻²⁰ kg

v = 0.50 µm/s = 5 *10⁻⁷ m/s

h = 6.62607*10^-9 Js

Virus size = 280 nm = 2.80*10⁻⁷ m

Substituting into the formula; we have

λ= h/(mv)

λ= 6.62607*10^-9/ (9.4*10⁻²⁰* 5 *10⁻⁷)

= 6.62607*10^-9/4.7*10^-26

= 1.4*10^17 m

Classical : Wavelength is bigger than it's size

(b)

A buckyball

m = 1.2 x 10-21 g = 1.2 *10⁻²⁴ kg

V = 37 m/s

Size = 0.7 nm = 7*10⁻¹⁰ m

Substituting into the formula, we have

λ= h/(mv)

λ= 6.62607*10^-9/ ( 1.2 *10⁻²⁴* 37)

= 6.62607*10^-9/4.44*10^-23

= 1.49 *10^14 m

Classical : Wavelength is bigger than it's size

(c)

A mosquito

Mass = 1.0 mg = 1*10⁻⁶ kg

v = 1.1 m/s

Size = 6.3 mm = 6.3*10⁻³ m

Substituting into the formula, we have

λ= h/(mv)

λ= 6.62607*10^-9/ ( 1*10⁻⁶* 1.1)

= 6.62607*10^-9/1.1*10^-6

= 6.02*10^-3 m

Quantum Approach: The wavelength and the size are comparable

(d)

A turtle

Mass = 710. g = 0.71 kg

Size = 22. cm = 0.22 m

V = 2.8 cm/s. = 0.028 m/s

Substituting into the formula, we have

λ= h/(mv)

λ= 6.62607*10^-9/ ( 0.71* 0.028)

= 6.62607*10^-9/0.01988

= 3.33*10^-7 m

Quantum Approach: The wavelength and the size are comparable

8 0

3 years ago

] A new coal-fired 750 MWe power plant with a thermal efficiency of 42% burns 9000 Btu/lb coal, which contains 1.1% sulfur. a. I

Valentin [98]

Answer:

The net emissions rate of sulfur is 1861 lb/hr

Explanation:

Given that:

The power or the power plant = 750 MWe

Since the power plant with a thermal efficiency of 42% (i.e. 0.42) burns 9000 Btu/lb coal, Then the energy released per one lb of the coal can be computed as:

$\mathtt{=( 0.42\times 9000\times 1055.06) J}$

= 3988126.8 J

= 3.99 MJ

Also, The mass of the burned coal per sec can be calculated by dividing the molecular weight of the power plant by the energy released per one lb.

i.e.

The mass of the coal that is burned per sec $=\dfrac{750}{3.99}$

The mass of the coal that is burned per sec = 187.97 lb/s

The mass of sulfur burned $= \dfrac{1.1}{100} \times 187.97 \ lb/s$

= 2.067 lb/s

To hour; we have:

= 7444 lb/hr

However, If a scrubber with 75% removal efficiency is utilized,

Then; the net emissions rate of sulfur is (1 - 0.75) × 7444 lb/hr

= 0.25 × 7444 lb/hr

= 1861 lb/hr

Hence, the net emissions rate of sulfur is 1861 lb/hr

8 0

2 years ago

Identify the velocity-versus-time plot(s) that correspond to motion under a constant, non-zero acceleration.

ICE Princess25 [194]

Answer:

See explanation

Explanation:

The question is incomplete because the images were not attached but I will try to help you as much as possible.

Constant acceleration implies that the velocity increases uniformly with time.

The graph of constant acceleration is a straight line graph having a slope. The slope of the graph is constant at any point along the straight line.

The image attached shows a velocity-time graph depicting constant acceleration.

5 0

3 years ago

A car is travelling at a speed of 30m/s on a straight road. what would be the speed of the car in km​

A car is travelling at a speed of 30m/s on a straight road. what would be the speed of the car in km