A person can run 400m in 72 s.. At what speed are they running

A 20.0 kg crate sits at rest at the bottom of a 15.0-m-long ramp that is inclined at 34.0° above horizontal. A constant horizont

ankoles [38]

Answer:

987 joules, 3.01s

Explanation:

(A)

from the attached diagram

net force, Fnet, pulling the crate up the ramp is given by

Fnet = FcosФ - WsinФ - Fr

where FcosФ is the component of horizontal force 290N resolved parallel to the plane

WsinФ = mgsinФ = component of the weight of the crate resolved parallel to the plane

Fr = constant opposing frictional force

Fnet = 290cos34⁰ - 20 × 9.8 × sin34° - 65

Fnet = 240.421 - 109.602 - 65

Fnet = 65.82N

Work done on the crate up the ramp, W, is given by

W = Fnet × d (distance up the plane)

W = 65.819 × 15

W = 987.285 joules

W = 987 joules (to 3 significant Figures)

(B)

to calculate the time of travel up the ramp

we use the equation of motion

$s = ut + \frac{1}{2}at^{2}$

where s = distance up the plane, 15m

u = Initial velocity of the crate, which is 0 for a body that is initially at rest

a = acceleration up the plane, given by

$a = \frac{Fnet}{m}$

where m = mass of the crate, 20 kg

now, $a = \frac{65.819}{20} \\a = 3.291\frac{m^{2} }{s}$

from, $s = ut + \frac{1}{2}at^{2}$

$15 = 0*t + \frac{1}{2}* 3.291 * t^{2}$

15 = 0 + 1.645 $t^{2}$

15 = 1.645 $t^{2}$

$t = \sqrt{\frac{15}{1.645} }$

$t = 3.019$

t = 3.01s (to 3 sig fig)

7 0

3 years ago

The aeroplane lands at a speed of 80 m/s

strojnjashka [21]

The mass of the aeroplane is 300,000 kg.

<h3>What is Newton's second law of motion?</h3>

It states that the force F is directly proportional to the acceleration a of the body and its mass.

The law is represented as

F =ma

where acceleration a = velocity change v / time interval t

Given is the aeroplane lands at a speed of 80 m/s. After landing, the aeroplane takes 28 s to decelerate to a speed of 10 m/s. The mean resultant force on the aeroplane as it decelerates is 750 000 N.

The force expression will be

F = mv/t

Substitute the values and we have

750000 = m x (80 -10)/ 28

750,000 = m x 2.5

m = 300,000 kg

Thus, the mass of the aeroplane is 300,000 kg.

Learn more about Newton's second law of motion.

brainly.com/question/13447525

#SPJ1

8 0

2 years ago

A polonium isotope with an atomic mass of 211.988868 u undergoes alpha decay, resulting in a daughter isotope with an atomic mas

prisoha [69]

Answer:

K = 9.53 MeV

Explanation:

The kinetic energy that the alpha particle has emitted, is the energy in excess after removing the resting energy of the atoms and the helium nucleus that forms the alpha particle

Since energy and masses are related and cannot be

m₀ c² = $m_{f}$ c² + m_He c²+ K

K = c² (m₀ - m_{f} - m_He)

the mass of the Helium atom is 4 u

K = (3 10⁸)² (211,988868 -207.976652 - 4,002) 1,661 10⁻²⁷

K = 14,949 10⁻¹¹ (0.0102)

K = 1,527 10⁻¹² J

let's reduce 1 J = 6,242 10¹² MeV

K = 9.53 MeV

7 0

3 years ago

Why does it matter if a material is amorphous or crystalline? How does the arrangement of atoms affect the properties of materia

Rashid [163]

Answer:

<em>It matters because crystalline and amorphous materials have different properties. The arrange affects the melting point (defined in crystals and a larger range in amorphous) and shape (geometrical in crystals, no geometrical in amorphous). </em>

Explanation:

The particles that compose a solid material are held in place by strong tractive forces between them when we analyze solids we consider the position of the atoms (molecules or ions) rather than their motion (which is important in liquids and gases). This positioning can be arranged in two general ways:

Crystalline solids have internal structures that in turn lead to distinctive flat surfaces or face, these faces intersect at angles that are characteristic of the substance, crystals tend to have sharp, well defined and high melting points because of the same distance from the same number and type of neighbors. They generally have geometric shapes, some examples are diamonds, metals, salts.
Amorphous solids produce irregular or curved surfaces when broken and they have poorly defined patterns when exposed to x rays because of their irregular array. In contrast with crystal solids, amorphous solids soften over a wide temperature range due to the different amounts of thermal energy needed to overcome different interactions. Some examples of these solids are gels, plastics, and some polymers.

I hope you find this information useful and interesting! Good luck!

8 0

3 years ago

The circuit below contains an ideal battery, four identical light bulbs, and a switch. The switch is initially open.

Dafna1 [17]

The question is incomplete! circuit figure is attached below and answer and explanation is provided below.

Answer:

Bulb_A = Bulb_B = Bulb_D and Bulb_C = 0.

Explanation:

What happens when switch is open?

When the switch is open Bulb_C is open circuited meaning that there is no way for the current to flow through it. This path offers infinite resistance to the current therefore, current will try to take a least resistance path that is through Bulb_B.

So eventually, when the switch is open the circuit becomes a simple series circuit with path From battery to Bulb_A to Bulb_B to Bulb_D to battery with Bulb_C = 0.

What happens in a series circuit?

We know that in a series circuit, there is only one path for the current to flow therefore, same current will flow through all the series Bulbs and their brightness will be same. Bulb_A = Bulb_B = Bulb_D

Brightness in a series circuit:

We also know know that in a series circuit, resistance gets summed up and voltage across each Bulb gets shared which results in less power dissipation that's why Bulbs connected in series appear dimmer as compared to when they are connected in parallel.

5 0

3 years ago