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tia_tia [17]
3 years ago
8

A woman can row a boat at 4.0 mph is still water.

Physics
1 answer:
vovikov84 [41]3 years ago
8 0

Answer:

1) \theta=120^{\circ} from the positive x-axis.

2) t=20\ min

Explanation:

Given:

speed of rowing in still water, v=4\ mph

1)

speed of water stream, v_s=2\ mph

we know that the direction of resultant of the two vectors is given by:

tan\ \beta=\frac{v.sin\ \theta}{v_s+v.cos\ \theta}

where:

\beta=the angle of resultant vector from the positive x-axis.

\theta = angle between the given vectors

When the rower wants to reach at the opposite end then:

\beta =90^{\circ}

so,

tan\ 90^{\circ}=\frac{v.sin\ \theta}{v_s+v.cos\ \theta}

\Rightarrow v_s+v.cos\ \theta=0

2+4\times cos\ \theta=0

cos\ \theta=-\frac{1}{2}

\theta=120^{\circ} from the positive x-axis.

2)

Now the resultant velocity of rowing in the stream:

v_r=\sqrt{v^2+v_s^2+2\times v.v_s.cos\ \theta}

v_r=\sqrt{4^2+2^2+2\times 4\times 2\times cos\ 120}

v_r=12\ mph

Therefore time taken to cross a 4 miles wide river:

t=\frac{4}{12}

t=\frac{1}{3}\ hr

t=20\ min

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konstantin123 [22]

The work done on the puck is 96 J

Explanation:

According to the work-energy theorem, the work done on the hockey puck is equal to the change in kinetic energy of the puck.

Mathematically:

W=K_f -K_i= \frac{1}{2}mv^2-\frac{1}{2}mu^2

where

K_f = \frac{1}{2}mv^2 is the final kinetic energy of the puck, with

m = 2 kg being the mass of the puck

v = 10 m/s is the final speed

K_i = \frac{1}{2}mu^2 is the initial kinetic energy of the puck, with

u = 2 m/s being the initial speed of the puck

Substituting numbers into the equation, we find the work done by the player on the puck:

W=\frac{1}{2}(2)(10)^2 - \frac{1}{2}(2)(2)^2=96 J

Learn more about work and kinetic energy:

brainly.com/question/6763771  

brainly.com/question/6443626  

brainly.com/question/6536722

#LearnwithBrainly

6 0
3 years ago
You wind a small paper tube uniformly with 153 turns of thin wire to form a solenoid. The tube\'s diameter is 5.11 mm and its le
lina2011 [118]

The concept required to solve this problem is linked to inductance. This can be defined as the product between the permeability in free space by the number of turns squared by the area over the length. Recall that Inductance is defined as the opposition of a conductive element to changes in the current flowing through it. Mathematically it can be described as

L = \frac{\mu N^2 A}{l}

Here,

\mu = Permeability at free space

N = Number of loops

A = Cross-sectional Area

l = Length

Replacing with our values we have,

L = \frac{(4\pi *10^{-7})(153)^2(\pi (\frac{5.11*10^{-3}}{2})^2)}{2.47*10^{-2}}

L = 0.00002442H

L = 24.42\mu H

Therefore the Inductance is 24.42\mu H

3 0
3 years ago
A nickel (5 cent coin) has a mass of 5.0 g. How many nickels are there in a stack of nickels with a mass of 10.0 kg?
Marrrta [24]

Answer:

2000 nickels

Explanation:

One way to solve proportionality problems, direct and inverse: the simple 3 rule.

If the relationship between the magnitudes is direct (when one magnitude increases so does the other), the simple direct rule of three must be applied.

On the contrary, if the relationship between the magnitudes is inverse (when one magnitude increases the other decreases) the rule of three simple inverse applies.

The simple 3 rule is an operation that helps us quickly solve proportionality problems, both direct and inverse.

To make a simple rule of three we need 3 data: two magnitudes proportional to each other, and a third magnitude. From these, we will find out the fourth term of proportionality.

In the simple three rule, therefore, the proportionality relationship between two known values ​​A and B is established, and knowing a third value C, a fourth value D is calculated.

A -> B

C -> D

Calculation

1 nickel --> 5 g

X? nickel --> 10000g

X = (10000 g * 1 nickel) / 5 g

X = 2000 nickels

7 0
3 years ago
The kinetic energy of the molecules inside the balloon _______ which
11111nata11111 [884]

Answer:

Increase,.faster

Explanation:

The kinetic energy of the molecules inside the balloon

increases

which means they are moving

faster

I hope this helps you :)

6 0
3 years ago
A standard 1 kilogram weight is a cylinder 54.0 mm in height and 55.0 mm in diameter. what is the density of the material
denis-greek [22]

The radius of the cylinder is equal to half the diameter:

r=\frac{d}{2}=\frac{55.0 mm}{2}=27.5 mm

The volume of the cylinder is given by:

V=\pi r^2 h=\pi (27.5 mm)^2 (54.0 mm)=1.28 \cdot 10^5 mm^3

where h is the heigth of the cylinder. Converting into meters,

V=1.28 \cdot 10^{-4} m^3

And the density of the material will be given by the ratio between the mass and the volume:

d=\frac{m}{V}=\frac{1 kg}{1.28 \cdot 10^{-4} m^3}=7812.5 kg/m^3

5 0
4 years ago
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