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Ludmilka [50]
3 years ago
11

Mary has a mass of 40 kg and sprints at 1 m/s. How much kinetic energy does she have?

Physics
1 answer:
Sav [38]3 years ago
8 0

Answer:

20 J

Explanation:

Kinetic energy is given as half of the product of mass and the square of velocity of an object:

KE = \frac{1}{2}mv^2

where m = mass = 40 kg

v = velocity = 1 m/s

Hence, Mary's kinetic energy is:

KE = \frac{1}{2} * 40 * 1^2

KE = 20 * 1 = 20 J

She has a kinetic energy of 20 J.

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Gold, which has a mass of 19.32 g for each cubic centimeter of volume, is the most ductile metal and can be pressed into a thin
Dennis_Churaev [7]

Answer:

area = 5733.33  cm²

length = 5.47 ×10^{7} cm

Explanation:

Given data

density = 19.32 g/cm³

mass = 33.16 g

thickness = 3.000 µm = 3 ×10^{-4} cm

radius r = 1.000 µm = 1 ×10^{-4} cm

to find out

area of the leaf and  length of the fiber

solution

we know volume formula that is

volume = mass / density

volume = 33.16 /  19.32

volume = 1.72 cm³

we know that volume = thickness × area

so area

area = volume / thickness

area = 1.72 / 3 ×10^{-4}

area = 5733.33  cm²

and

we know volume = πr²L

so L = volume /  πr²

length = 1.72 / π(1×10^{-4})²

length = 5.47 ×10^{7} cm

3 0
3 years ago
What is the speed of the animal from 0-20s? <br><br> 50 m/s<br> 0.4 m/s<br> 20 m/s<br> 2.5 m/s
Shkiper50 [21]

Answer:

2.5 m/s

Explanation:

The speed of the animal is given by the ratio between the distance travelled by the animal and the time elapsed:

v=\frac{d}{t}

where d is the distance travelled and t the time elapsed. Note that this quantity is also equal to the slope of the curve.

In the time interval 0-20 s, we have

d = 50 m - 0 m = 50 m

t = 20 s - 0 s = 20 s

So, the speed is

v=\frac{50 m}{20 s}=2.5 m/s

3 0
3 years ago
The knee extensors insert on the tibia at an angle of 30 degrees (from the longitudinal axis of the tibia), at a distance of 3 c
Reika [66]

Answer:

the knee extensors must exert 15.87 N

Explanation:

Given the data in the question;

mass m = 4.5 kg

radius of gyration k = 23 cm = 0.23 m

angle ∅ = 30°

∝ = 1 rad/s²

distance of 3 cm from the axis of rotation at the knee r = 3 cm = 0.03 m

using the expression;

ζ = I∝

ζ = mk²∝

we substitute

ζ = 4.5 × (0.23)² × 1

ζ  = 0.23805 N-m

so

from; ζ = rFsin∅

F = ζ / rsin∅

we substitute

F = 0.23805 / (0.03 × sin( 30 ° )

F = 0.23805 / (0.03 × 0.5)

F F = 0.23805 / 0.015

F = 15.87 N

Therefore, the knee extensors must exert 15.87 N

7 0
3 years ago
20. Using the picture, how many neutrons does lithium have?
Igoryamba

Answer:

No. of Neutrons = 3

Explanation:

The atomic number of Lithium is given as 3 in the symbol while the mass number is given as 5.941 which is approximately equal to 6.

Mass Number = No. of Protons + No. of Neutrons = 6

Atomic Number = Number of Electrons = No. of Protons = 3

Therefore,

Mass Number - Atomic Number = (No. of Protons + No. of Neutrons) - No. of Protons

Mass Number - Atomic Number = No. of Neutrons

No. of Neutrons = 6 - 3

<u>No. of Neutrons = 3 </u>

8 0
3 years ago
This is a velocity versus time graph of a car starting from rest. If the area under the line is 10 meters, what is the correspon
adelina 88 [10]

So the area under a velocity time graph is distance or displacement, if you have done calculus yet you will understand that if you take the integral of a velocity function then you end up with displacement. Thats for later understanding however.

So this appears to be a right triangle so we can find the area of a triangle as:

0.5bh = A

Since our area is 10 meters lets alter our formula a bit to fit the situation:

Our base here is time and our height is velocity so:

0.5tv = Δx

So we can read off the graph that our velocity at the end, or our final velocity appears to be near 2.0 m/s

So we have v, and Δx so lets isolate for time by dividing by v and 0.5

t = Δx / 0.5v

Now lets plug all that in:

t = 10 / 0.5(2)

t = 10 seconds

Hope this helped!

8 0
3 years ago
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