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3 years ago

What purpose does a female pine cone serve?

Physics

2 answers:

erma4kov [3.2K]3 years ago

7 0

protects the seeds until it matures

Dimas [21]3 years ago

5 0

The answer is It protects the seed until it matures.

Through the process of elimination:
- It protects the seed until it matures. YES. A female pine cone the unfertilized seeds until they become mature. Then, the cone opens and seeds fall out of the cone.

- It makes food for the adult plant. NO. The food of plants in made of green leaves that contain chlorophyll in the process of photosynthesis.
- It allows for photosynthesis to occur. NO. The cones have nothing to do with photosynthesis but they are responsible for reproduction.
- It acts as an object to attract birds. NO. The birds look for colourful flowers while cones are woody.
- It serves as an ornamental object on the tree. NO. Every part of plants has more important function than serving as an ornamental object.

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A 80 kg skier grips a moving rope that is powered by an engine and is pulled at constant speed to the top of a 25 degrees hill.

zloy xaker [14]

Answer:

$P=28.085\,hp$

Explanation:

Given that:

mass of 1 skier, $m=80kg$

inclination of hill, $\theta=25^{\circ}$

length of inclined slope, $l=220m$

time taken to reach the top of hill, $t=2.3 min= 138 s$

coefficient of friction, $\mu=0.15$

Now, force normal to the inclined plane:

$F_N=m.g.cos\theta$

$F_N=80\times 9.8\times cos25^{\circ}$

$F_N=710.54\,N$

Frictional force:

$f=\mu.F_N$

$f=0.15\times 710.54$

$f=106.58\,N$

The component of weight along the inclined plane:

$W_l=m.g.sin\theta$

$W_l=80\times 9.8\times sin25^{\circ}$

$W_l=331.33\,N$

Now the total force required along the inclination to move at the top of hill:

$F=f+W_l$

$F=106.58+331.33$

$F=437.91\,N$

Hence the work done:

$W=F.l$

$W=437.91\times 220$

$W=96340.80\,J$

Now power:

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

$P=\frac{96340.80}{138}$

$P=698.12\,W$

So, power required for 30 such bodies:

$P=30\times 698.12$

$P=20943.65\,W$

$P=\frac{20943.65}{745.7}$

$P=28.085\,hp$

8 0

3 years ago

You're driving at 50 mph and then speed up to 70 mph. how much more "force" does the engine in your car have to produce to maint

Fittoniya [83]

You drove 20 more mph than what you did before. The more force is 20 because you drove 20 more mph.

6 0

3 years ago

If A vector = i^-j^+k^ then unit vector in the direction of A vector

Novosadov [1.4K]

If A = i - j + k, then the magnitude of A is

||A|| = √(1² + (-1)² + 1²) = √3

Then the unit vector in the direction of A is 1/||A|| multiplied by A :

u = A/||A|| = (i - j + k)/√3

(choice D)

6 0

3 years ago

On a horizontal frictionless surface a mass M is attached to two light elastic strings both having length l and both made of the

EastWind [94]

Answer:

ω = √(2T / (mL))

Explanation:

(a) Draw a free body diagram of the mass. There are two tension forces, one pulling down and left, the other pulling down and right.

The x-components of the tension forces cancel each other out, so the net force is in the y direction:

∑F = -2T sin θ, where θ is the angle from the horizontal.

For small angles, sin θ ≈ tan θ.

∑F = -2T tan θ

∑F = -2T (Δy / L)

(b) For a spring, the restoring force is F = -kx, and the frequency is ω = √(k/m). (This is derived by solving a second order differential equation.)

In this case, k = 2T/L, so the frequency is:

ω = √((2T/L) / m)

ω = √(2T / (mL))

6 0

4 years ago

2. A small piece of dust is located in between two oppositely charged parallel plates where there exists a uniform electric fiel

Alla [95]

Answer:

The total charge is $q = 1.6*10^{-4}C$

The change in potential energy is $\Delta U = -4*10^{-2}J$

The height is $h= 8.2cm$

Explanation:

From the question we are told that the

The magnitude of electric field is $E = 5000N/C$

The number of proton is $N_p = 1*10^{15}$

The distance between the plates is $d = 5cm = \frac{5}{100} = 0.05m$

The total charge can be mathematically represented as

$q = N_p * e$

Where e is the charge on one proton which has a value of $=1.6*10^{-19}C$

Substituting values

$q = 1 *10^{15} * 1.6*10^{-19} = 1.6 *10^{-4}C$

The change in potential energy is mathematically represented ads

$\Delta U = -(qE)d$

where the negative sign shows that the work done by the electric force is against the electric field

Substituting values

$\Delta U = - 1.6*10^{-4} * 5000 * 0.05$

$= -4*10^{-2}J$

The mass of the bead is given as 0.05kg

The change in potential due to gravity is mathematically given as

$\Delta U = -mgh$

the negative sign is due to the fact that the height is decreasing

And $g =9.8m/s^2$

Making h the subject

$h = \frac{\Delta U}{mg}$

Substituting values

$h = \frac{4*10^{-2}}{0.05 * 9.8}$

$=0.081m = 0.082 *100 = 8.2cm$

4 0

4 years ago