Ask question

Ask question

All categories

tankabanditka [31]

4 years ago

9

An archerfish, peering from just below the water surface, sees a grasshopper standing on a tree branch that's just above the wat

er. The archerfish spits a drop of water at the grasshopper and knocks it into the water. The grasshopper's initial position is 0.45 m above the water surface and 0.25 m horizontally away from the fish's mouth. The launch angle of the drop is 63° with respect to the water surface. Anticipating that the grasshopper would do this, the archerfish decides to spit the water at a higher speed but at the same launch angle (63°). At what speed should the archerfish spit the water for the drop to hit the grasshopper?

1 answer:

Mariana [72]4 years ago

4 0

Answer:

Explanation:

let the velocity of throw is u .

Time to reach horizontally .25 m is equal to reach .45 m vertically

t = .25 / u cos63

= .55 / u

For vertical motion

- h = - ut + 1/2 gt²

-.45 = -usin63 x .55 / u + .5 x9.8 (.55 / u )²

-.45 = - .49 + 1.48 / u²

.04 = 1.48 / u²

u² = 37

u = 6.08 m /s

You might be interested in

Potassium is a crucial element for the healthy operation of the human body. Potassium occurs naturally in our environment and th

gregori [183]

Complete Question

Potassium is a crucial element for the healthy operation of the human body. Potassium occurs naturally in our environment and thus our bodies) as three isotopes: Potassium-39, Potassium-40, and Potassium-41. Their current abundances are 93.26%, 0.012% and 6.728%. A typical human body contains about 3.0 grams of Potassium per kilogram of body mass. 1. How much Potassium-40 is present in a person with a mass of 80 kg? 2. If, on average, the decay of Potassium-40 results in 1.10 MeV of energy absorbed, determine the effective dose (in Sieverts) per year due to Potassium-40 in an 80- kg body. Assume an RBE of 1.2. The half-life of Potassium-40 is $1.28 * 10^9$ years.

Answer:

The potassium-40 present in 80 kg is $Z = 0.0288 *10^{-3}\ kg$

The effective dose absorbed per year is $x = 2.06 *10^{-24}$ per year

Explanation:

From the question we are told that

The mass of potassium in 1 kg of human body is $m = 3g= \frac{3}{1000} = 3*10^{-3} \ kg$

The mass of the person is $M = 80 \ kg$

The abundance of Potassium-39 is 93.26%

The abundance of Potassium-40 is 0.012%

The abundance of Potassium-41 is 6.78 %

The energy absorbed is $E = 1.10MeV = 1.10 *10^{6} * 1.602 *10^{-19} = 1.7622*10^{-13} J$

Now 1 kg of human body contains $3.0*10^{-3}\ kg$ of Potassium

So 80 kg of human body contains k kg of Potassium

=> $k = \frac{ 80 * 3*10^{-3}}{1}$

$k = 0.240\ kg$

Now from the question potassium-40 is 0.012% of the total potassium so

Amount of potassium-40 present is mathematically represented as

$Z = \frac{0.012}{100} * 0.240$

$Z = 0.0288 *10^{-3}\ kg$

The effective dose (in Sieverts) per year due to Potassium-40 in an 80- kg body is mathematically evaluated as

$D = \frac{E}{M}$

Substituting values

$D = \frac{1.7622*10^{-13}}{80}$

$D = 2.2*10^{-15} J/kg$

Converting to Sieverts

We have

$D_s = REB * D$

$D_s = 1.2 * 2.2 *10^{-15}$

$D_s = 2.64 *10^{-15}$

So

for half-life ( $1.28 *10^9 \ years$ ) the dose is $2.64 *10^{-15}$

Then for 1 year the dose would be x

=> $x = \frac{2.64 *10^{-15}}{1.28 * 10^9}$

$x = 2.06 *10^{-24}$ per year

7 0

4 years ago

Why should scientist data be written in ink ? I need major help plz :)

Kobotan [32]

Because they are legal documents they can be used in a court of law

3 0

3 years ago

What two types of scientific knowledge can be expressed as mathematical equations

melamori03 [73]

Mathematical equations can express dependencies between things, for example the relationship between the speed and acceleration. This can be summarized under "scientific laws".

More complex laws can represent models, for example a model of a human brain on a neuronal level could be based on complex mathematical equations.

7 0

4 years ago

Read 2 more answers

The driver of a car slams on the brakes, causing the car to slow down at a rate of 17ft/s2 as the car skids 285ft to a stop.

ozzi

1) 5.79 s

2) 98.4 ft/s

Explanation:

1)

The motion of the car is a uniformly accelerated motion (it means it travels with constant acceleration), so we can find the time it takes for the car to stop by using the following suvat equation:

$s=vt-\frac{1}{2}at^2$

where

s is the distance travelled

v is the final velocity

t is the time

a is the acceleration of the car

In this problem we have:

s = 285 ft is the distance travelled

$a=-17 ft/s^2$ is the acceleration of the car (negative since the car is slowing down)

v = 0 ft/s is the final velocity of the car, since it comes to a stop

Solving for t, we find:

$t=\sqrt{\frac{-2s}{a}}=\sqrt{\frac{-2(285)}{-17}}=5.79 s$

2)

The initial speed of the car can be found by using another suvat equation, namely:

$v=u+at$

where

v is the final speed

u is the initial speed

a is the acceleration

t is the time

In this problem, we have:

v = 0 is the final speed of the car

$a=-17 ft/s^2$ is the acceleration of the car (negative since the car is slowing down)

t = 5.79 s is the total time of motion (found in part 1)

Therefore, the initial speed of the car is:

$u=v-at=0-(-17)(5.79)=98.4 ft/s$

8 0

3 years ago

A block requires an applied force of 20N to begin moving it to the right. What is the maximum static friction?

dangina [55]

Answer:

A.

Explanation:

Thats my answer

Please make me branlies answer

4 0

3 years ago