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3 years ago

What occurs when a swimmer pushes through the water to swim?

2 answers:

6 0

When a swimmer pushes threw water to swim they are propelled forward because of the water resistance against the hand and feet.

ehidna [41]3 years ago

4 0

The correct answer to the question is that water will exert a force on the swimmer in forward direction, and swimmer will move along that direction.

EXPLANATION:

Before going to answer this question, first we have to understand Newton's third laws of motion.

Newton's third laws of motion states that, for every action, there is an equal and opposite reaction.

In the given question, the swimmer pushes the water in backward direction. This is the force of action. As per Newton's third law, the water must exert a reaction on the swimmer. The water applies a force on the swimmer in forward direction for which the swimmer can swim in the water.

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Newton s third law of motion states that every action has an __________ but __________ reaction.

Margaret [11]

Newton´s thrid law of motion states that:
Every action has an equal and opposite reaction.

c. equal, opposite.

3 0

3 years ago

A car moving with a speed of 35 m/s sees a child standing in the

zlopas [31]

Answer:

2100 N

Explanation:

$v = u + at \\ 0 = 35 + a(5) \\ a = - 7m {s}^{ - 2} \\ \\ net \: force \: = ma \\ = (300)(7) \\ = 2100 \: newtons$

6 0

2 years ago

When you're asked to calculate moments and torque, what's the main difference in calculation? Also what is a couple?

leva [86]

Answer:

a) Explanation below. b) Explanation below

Explanation:

Torque is defined as the product of a force by a radius, while momentum is defined as the product of force by a distance. Mathematically we would have

T = F * r

M = F * d

where:

T = torque = [N*m]

M = moment = [N*m]

F = force =[N]

d = distance [m]

r = radius [m]

Although they have the same units, the difference between them is the application. For the case of torque this is always applied in parts that are in rotation, such as the shafts of cars, the shafts of pumps, torque in gears and etc. While the moment can be applied to a body without the need for it to rotate.

A couple, is as its name suggests a couple of forces of equal magnitude but opposite sense and do not share a line of action. A body under the action of a couple of forces tends to rotate the body without moving it from one point to another.

7 0

3 years ago

An alternator consists of a coil of area A with N turns that rotates in a uniform field B around a diameter perpendicular to the

svet-max [94.6K]

Answer:

(a): emf = $\rm 2\pi f NBA\sin(2\pi ft).$

(b): Amplitude of alternating voltage = 20.942 Volts.

Explanation:

<u>Given:</u>

Area of the coil = A.
Number of turns of coil = N.
Magnetic field = B
Rotation frequency = f.

(a):

The magnetic flux through the coil is given by

$\phi = \vec B \cdot \vec A=BA\cos\theta$

where,

$\vec A$ = area vector of the coil directed along the normal to the plane of the coil.

$\theta$ = angle between $\vec B$ and $\vec A$ .

Assuming, the direction of magnetic field is along the normal to the plane of the coil initially.

At any time t, the angle which magnetic field makes with the normal to the plane of the coil is $2\pi ft$

Therefore, the magnetic flux linked with the coil at any time t is given by

$\phi(t) = NBA\cos(2\pi ft)$

According to Faraday's law of electromagnetic induction, the emf induced in the coil is given by

$e=-\dfrac{d\phi}{dt}\\=-\dfrac{d(NBA\cos(2\pi ft))}{dt}\\=-NBA(-2\pi f\sin(2\pi ft))\\=2\pi f NBA\sin(2\pi ft).$

(b):

The amplitude of the alternating voltage is the maximum value of the emf and emf is maximum when $\sin(2\pi ft)=1.$

Therefore, the amplitude of the alternating voltage is given by

$e_o = 2\pi ft NBA.$

We have,

$N=100\\A=10^{-2}\ m^2\\B=0.1\ T\\f=2000\ rev/ min = 2000\times \dfrac{1}{60}\ rev/sec=33.33\ rev/sec.$

Putting all these values,

$e_o = 2\pi \times 33.33\times 100\times 0.1\times 10^{-2}=20.942\ Volts.$

7 0

3 years ago

Please help, my homework is due in a couple of days and I'm stuck. A plane is travelling 10.0 meters per second (this means the

ss7ja [257]

Answer:

< 25 m/s
triangle inequality
between north and east
45° < angle < 60°

Explanation:

(a) Just as one-dimensional numbers add on a number line by putting them end-to-end, so two-dimensional numbers add on a coordinate plane the same way.

Here, we choose to let the positive y-axis represent North, and the positive x-axis, East. This is the way a map is conventionally oriented. The velocity of the plane is represented by a vector pointing north (up). Its length represents the magnitude of the velocity. Likewise, the wind is represented by a vector of length 15 pointing east (right). The sum of these is the hypotenuse of the triangle they form.

The magnitude of the sum can be found here using the Pythagorean theorem, but for the purpose of this question, you're not asked to find that.

Instead, you're asked to estimate whether it is more or less than 25 (m/s).

Your knowledge of the triangle inequality will tell you that the hypotenuse (resultant) must be shorter than the sum of the lengths of the sides of the triangle, hence must be less than 10+15 = 25.

(b) The triangle inequality says the resultant is less than the sum of the other two sides of the triangle.

(c) Since the wind is blowing the plane toward the east, but the plane is traveling toward the north, the resulting direction is somewhere between north and east.

(d) "Somewhere between north and east" can be expressed as the inequality ...

0° < angle < 90°

4 0

3 years ago