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1 year ago

Which of the following agricultural advancements have had unforeseen adverse effects?

Physics

2 answers:

GuDViN [60]1 year ago

6 0

Answer:

use of pesticides increasing insect resistance

Explanation:

kobusy [5.1K]1 year ago

3 0

Answer:

use of pesticides increasing insect resistance

Explanation:

Pesticides are the chemicals used to kill or stop the growth of insects or pests in crops and plants.

Pesticides are used from a very long time and repeated use of same pesticide allowed insects to get use to of it and evolve themselves in a way that they become resistant to these pesticide, so pesticide do not have any effect on insects.

Hence, the correct answer is "use of pesticides increasing insect resistance".

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A steel cable 1.25 in. in diameter and 50 ft long is to lift a 20-ton load without permanently deforming. What is the length of

Over [174]

Answer:

50.0543248872 ft

Explanation:

F = Load = 20 ton = $20\times 2000\ lb$

d = Diameter = 1.25 in

$L_1$ = Initial length = 50 ft

$L_2$ = Final length

A = Area = $\dfrac{\pi}{4}d^2$

Y = Young's modulus = $30\times 10^6\ psi$

Young's modulus is given by

$Y=\dfrac{FL}{A\Delta L}\\\Rightarrow Y=\dfrac{FL_1}{\dfrac{\pi}{4}d^2(L_2-L_1)}\\\Rightarrow L_2=\dfrac{4FL_1}{Y\pi d^2}+L_1\\\Rightarrow L_2=\dfrac{4\times 40000\times 50}{30\times 10^6\times \pi\times 1.25^2}+50\\\Rightarrow L_2=50.0543248872\ ft$

The length during the lift is 50.0543248872 ft

6 0

2 years ago

Sarah is 14 years old and skips school twice a week without any written explanation. What can she be charged with?

harina [27]

Answer:

Too many people are unaware or indifferent to that.” Fines can cost up to $500 per truancy, due within 30 days unless a judge gives an extension. For many students and families, it's another debt they can't pay. And if fines aren't paid, they can convert into an arrest warrant when a student turns 17.

Explanation:

5 0

2 years ago

Light-rail passenger trains that provide transportation within and between cities speed up and slow down with a nearly constant

rosijanka [135]

Answer:

$v_f = 13m/s + 0.75 \frac{m}{s^2} * 16 s= 13 m/s +12m/s = 25 m/s$

Explanation:

For this case we know that the initial velocity is given by:

$v_i = 7 \frac{m}{s}$

The final velocity on this case is given by:

$v_f = 13 \frac{m}{s}$

And we know that it takes 8 seconds to go from 7m/s to 13m/s. We can use the following kinematic formula in order to find the acceleration during the first interval:

$v_f = v_i +at$

If we solve for the acceleration we got:

$a = \frac{v_f -v_i}{t} = \frac{13 m/s -7 m/s}{8 s}= 0.75 \frac{m}{s^2}$

So for the other traject we assume that the acceleration is constant and the train travels for 16 s. The initial velocity on this case would be 13m/s from the first interval and we can find the final velocity with the following formula:

$v_f = v_ i +a t$

And if we replace we got:

$v_f = 13m/s + 0.75 \frac{m}{s^2} * 16 s= 13 m/s +12m/s = 25 m/s$

5 0

2 years ago

A block of mass 1.6 kg is attached to a horizontal spring that has a spring constant of 1,000 LaTeX: \frac{N}{m}N m. The spring

mrs_skeptik [129]

Answer:

3.52 m/s

Explanation:

work done by the compressing the spring = 1/2 K e² where K is the force constant = 1000 N/m, e is the compression = 2cm = (2 / 100) to convert it to m we divide by 100 = 0.02 m

work done by compressing the spring = elastic potential energy stored in the spring = 0.5 × 1000 × 0.02 = 10 J

work done by force of friction to hinder the motion = F × d = 4 × 0.02 m = 0.08 J

Kinetic energy of the body = work done by compressing the spring - work done by force of friction against the motion = 10 - 0.08 = 9.92

9.92 = 1/2 m v² where m is the mass of the body which = 1.6 kg and v is the speed as it passes through the equilibrium point

9.92 = 1/2 × 1.6 × v²

9.92 × 2 / 1.6 = v²

v² = 19.84 / 1.6 = 12.4

v = √12.4 = 3.52 m/s

3 0

2 years ago

A man takes 20 seconds to climb 5m up a ladder. He weighs 720N. Calculate the power he must deliver to do this.

muminat

Answer:

Power = 180 Watt.

Explanation:

W = Work done = m x g x H.

m = mass of the body.

g = acceleration due to gravity = 9.8 m/s^2.

W = weight of the body = m x g = 720 N.

H = height of the body = 5 m.

t = Time = 20 s.

Plugging the above values in the formula we get:

W = 720 x 5 = 3600 J.

Power = $\frac{W}{t}$

= $\frac{3600}{20}$ = 180 Watt.

Therefore the required value of power = 180 Watt.

5 0

2 years ago