Mary needs to row her boat across a 140 m-wide
river that is flowing to the east at a speed of
1.5 m/s. Mary can row with a speed of 4.0 m/s.

The work done when pushing a desk is (W)= 47.6 Joules

When an object is moved over a distance by an external force at least part of which is applied in the direction of the displacement that explains that the work done on a object.

To calculate the values of the work done we are using the formula,

W = F×d

Here, we are given,

F = Exerted Force =28N

d = Covered Distance  in the desk =1.7m

We have to calculate,

W = Work done, unit in Nm or joules

Now we put the known values in the above equation, we get,

W = F×d

Or, W = (28N)×(1.7m)

Or, W = 47.6 Nm

Or, W = 47.6 Joules

Now we can say that,

The work done when pushing a desk is (W)= 47.6 Joules

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The total energy of the coaster at that point is 1274000 J.

Energy can be defined as the ability or the capacity for a body to perform work.

From the question, to calculate the total energy of the coaster at that point, we use the formula below.

Formula:

Where:

From the question,

Given:

Substitute the values above into equation 1

Hence, the total energy of the coaster at that point is 1274000 J.

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The Snell's law is also known as second law of refraction.

According to the Snell's law , the ratio of the sine of angle of incidence to the sine angle of refraction is equal to a constant of a light ray for two media . And it is given as,

[tex]\frac{sini}{sinr} = constant[/tex]

Where, [tex]sin i[/tex] is the angle of incidence light ray, [tex]sinr[/tex] is the angle of refracted light ray. Refractive index, also known as this constant and referred to as the second medium with respect to the first medium i.e. (₁μ₂) ,therefore the equation can be written as,

μ₁/μ₂ = ₁μ₂= [tex]\frac{sini}{sinr} = constant[/tex]

Refraction is a phenomena in which a light ray bends as it travels through one medium through another .

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The direction of the given vector B of 18.6 m that is 80° left of the positive y-axis is 170°

Angle of the vector made with positive y-axis = 80°

Angle between positive x and y axis = 90°

Direction of B, θ = 90° + 80°

θ = 170°

Direction of a vector is the angle of the vector that is made with positive x-axis. A vector with a certain direction of certain degrees means that the vector is rotated that much degrees in counter-clockwise direction relative to positive x-axis.

Therefore, the direction of the vector B is 170°

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Answer:

See below

Explanation:

The force of friction is opposite to the force trying to move the block to the right....

The equation we use is to determine the acceleration of the car, it is a Uniformly Varied Rectilinear Motion (MRUV) is:

             [tex]\boxed{\sf{a=\dfrac{V_{f}-V_{o}}{t}}} \ \ \ \ \ \sf{\longmapsto \ \ \ \ \ Where \ \ \ \ \begin{cases}\sf{V_{f} = Final \ velocity} \\ \sf{V_{o}=Initial \ velocity} \\ \sf{a=Acceleration} \\ \sf{t=Time} \end{cases}}[/tex]

We extract the data of the problem:

We plug these values into the scalar equation above.

                                         [tex]\sf{a=\dfrac{V_{f}-V_{o}}{t}}[/tex]

                                   [tex]\sf{a=\dfrac{20 \ m/s-40m/s}{10 \ s} }[/tex]

                                          [tex]\sf{a=\dfrac{-20 \ m/s}{10 \ s} }[/tex]

                                         [tex]\boxed{\boxed{\boldsymbol{\sf{a=-2 \ m/s^{2} }}}}[/tex]

Rpta: The acceleration of the car was -2 m/s^2.

The player’s initial velocity, given the data from the question is 15.68 m/s

We'll begin by obtaining the time taken for the player to reach the maximum height. This can be obtannnned as follow:

T = 2t

3.2 = 2t

Divide both sides by 2

t = 3.2 / 2

t = 1.6 s

v = u + gt

0 = u + (-9.8 × 1.6)

0 = u - 15.68

Collect like terms

u = 0 + 15.68

u = 15.68 m/s

Thus, the initial velocity of the player is 15.68 m/s

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The volume of the rock with a density of 45 g/mL and a mass of 855 grams is 19 ml

We know that,

ρ = m / V

where,

ρ = Density

m = Mass

V = Volume

Given that,

ρ = 45 g / ml

m = 855 g

V = 855 / 45

V = 19 ml

Density is the measure of amount of molecules present in substance. It is denoted by ρ. Its unit is usually g / ml.

Therefore, the volume of the rock with a density of 45 g/mL and a mass of 855 grams is 19 ml

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Answer: Inferring,Predicting,Analyzing

if this wasn't what you were looking for, here are some more science skills to help you pass you classes

- Evaluating.

- Generating possibilities.

- Formulating hypothesis.

- Communicating

Explanation: all these science skills will help you get through your science class with no struggles

Answer:

They are attracted to each other. Maybe a magnet. Like 99% sure.

Explanation:

Objects that are usually attracted to each other are magnets. When you release two magnets close to each other, with each pole opposite to the other, they move toward each other and stick. You can only take them apart by force.

Explanation:

These "more energetic particles" may have

sufficient energy to escape from the surface

of the liquid as gas or vapour.... Evaporation

takes place at room temperature which is

often well below the boiling point of the

liquid. Evaporation happens from the surface

of the liquid.

The maximum number of chips is 33,333

What is a chip?

A chip is a tiny but complex modules that store computer memory or provide logic circuitry for microprocessors.

We need to find the number of wafers that can be cut from a single crystal.

The crystal is 25cm and each wafer is 0.3mm. We perform division to get the number of wafers per crystal after getting everything into the same units. 25cm=250mm.

250mm/0.3mm=833.3333 wafers.

Each wafer yields 400 chips so we multiply 400 chips per wafer by 833.33 wafers to get 33,333 chips.

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The final charge on each object is -1.6μC.

Each metallic object has 10^13 electrons on it.

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The speed of the river current with respect to the boat is(Vₙ)=  1.036 m/s.

Speed is a scalar quantity. Speed is a way of measuring how quickly something is moving or being done, or something moving fast.

To calculate the values of the speed of the river, we are using the formula,

v=1.768-Vₙ

The given parameters;

boat's speed ,  vₐ= 2.5 m/s

the river's width, w = 285 m

upstream distance , d = 118 m

the pilot's direction, θ = 45⁰

We know the velocity has the vertical and horizontal component, so we can calculate this ;

v(x)=vₐsinθ=2.5*sin45°=1.768m/s

v(y)=vₐcosθ=2.5*cos45°=1.768m/s

To calculate the time taken for the boat is  ;

t=w/v(y)

Or, t=285/1.768

Or, t = 161.25 s

To calculate the total horizontal velocity of the boat and the river; we are using the formula,

v=1.768-Vₙ

Or,1.768-Vₙ=d/t

Or, 1.768-Vₙ=118/161.2

Or, 1.768-Vₙ=0.732

Or, Vₙ=1.036m/s

From the above calculation we can conclude that,

The speed of the river current with respect to the boat is 1.036 m/s.

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Note: The question is incomplete in the portal. Here is the total question,

Question: A boat, whose speed in still water is 2.50 m/s, must cross a 285-m wide river and arrive at a point 118m upstream from where it starts. To do so, the pilot must head the boat at a 45.0 degrees upstream angle. What is the speed of the rivers current?

Answer:

380 to 700 nanometers.

Explanation:

Magnus effect generates lift on a Flettner rotor. It is named as Magnus effect, as it was first experimentally investigated by H G Magnus.

A Flettner rotor is a smooth cylinder with a disc plate at the end of it. The disc at the end is called as Thom disc. It optimses aerodynamic efficiency at the end of rotor. The rotor is rotated along its axis by the ship's engines. It is used in ships and airplanes. In ships it is mounted upright whereas in airplanes it is mounted sideways in place of wings.

As air strikes the rotating rotor at right angles to the axis of rotor, the ship moves in the direction perpendicular to both the rotation axis and air flow direction due to aerodynamic force created by Magnus effect.

Therefore, Magnus effect generates lift on a Flettner rotor.

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Answer:

A alkali metals hope this helps

Answer: c. alkaline earth metal

Explanation: group II elements in the periodic table are generally found as 2+ ions.  This is because they have lost two electrons to ionic bonding.

Answer:

Explanation:

A simple machine is the simplest device that performs work. A simple machine applies a single force to a single load and generally acts as a building block in developing more complex, compound machines. Simple machines usually fall into one of six categories, including: lever, wheel and axle, pulley, inclined plane, wedge and the screw.

I hope this helps you ")

Heat transfer by radiation and convection causes the surface water of the pool to be warm which decreases with depth.

There are two heat transfer process responsible for variation in temperature of water at different depth of a pool, they include;

The surface of the water absorbs heat from the air and the sun. The heat from the sun is transferred to the pool through radiation.

The heat from the air is transferred to the pool through convection.

Thus, these two heat transfer processes  causes the surface water of the pool to be warm which decreases with depth.

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The height above the ground reached by the rock is 7.7 m.

The time taken for the rock to travel half of a second after it is released is 1.12 seconds.

The velocity of the rock half of a second after it is released is 15.9 m/s.

The velocity of the rock 1.5 seconds after release is 25.7 m/s.

The vertical height traveled by the rock is calculated as follows;

h = u²/2g

h = (11²)/(2 x 9.8)

h = 6.2 m

Height above the ground reached by the rock = 1.5 m + 6.2 m = 7.7 m

t = √2h/g

t = √(2 x 6.2/9.8)

t = 1.12 seconds

v = u + gt

v = 11 m/s   +  (9.5 x 0.5)

v = 15.9 m/s

v = u + gt

v = 11 m/s   +  (9.5 x 1.5)

v = 25.7 m/s

Thus, the height above the ground reached by the rock is 7.7 m.

The time taken for the rock to travel half of a second after it is released is 1.12 seconds.

The velocity of the rock half of a second after it is released is 15.9 m/s.

The velocity of the rock 1.5 seconds after release is 25.7 m/s.

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The magnitude of the average force applied to the ball is 104.98 N

Momentum is defined as the product of mass and velocity. It is expressed as

Momentum = mass × velocity

This is defined as the change in momentum of an object.

Impulse = change in momentum

Impulse = final moment – Initial momentum

But

Impulse = force × time

Therefore

Force × time = final moment – Initial momentum

Ft = m(v - u)

Ft = m(v + u) (rebound )

Divide both sides by t

F = m(v + u) / t

F = [0.17 × (17.1 + 23.1)] / 0.0651

F = [0.17 × 40.2] / 0.0651

F = 6.834 / 0.0651

F = 104.98 N

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The volume of a rock with a density of 45 g/mL and a mass of 855g is 19mL.

The volume of a gas can be calculated by dividing the mass of the substance by its density as follows:

Volume = mass ÷ density

According to this question, a rock has a density of 45 g/mL and a mass of 855g. The volume can be calculated as follows:

Volume = 855g ÷ 45g/mL

Volume = 19mL

Therefore, the volume of a rock with a density of 45 g/mL and a mass of 855g is 19mL.

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Velocity of the ball by which it hits the ground is 5.721 m/s.

Height from which the ball has been thrown, s = 1.67m

Acceleration due to gravity, g = 9.81 m/s²

Since, velocity of the ball hitting the ground is being asked, rebound height can be ignored.

So according to the Third Equation of Motion which relates velocity, displacement and acceleration, we can find the velocity of the ball,

[tex]v^{2} = u^{2} + 2as[/tex]

u = initial velocity of the ball = 0 m/s

v² = 0 +2*(-9.8)*(-1.67)

v² =  32.732 m/s

[tex]v = \sqrt{32.732}[/tex] m/s

v = -5.721 m/s

Square root of velocity (v) will give two values, one as positive and the other as negative, and here negative value is considered because the velocity is towards the ground and downwards is taken here as negative.

Therefore the velocity of the ball hitting the ground will be 5.721 m/s.

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A. The distance travelled after 53.3 seconds is 1919.63 m

B. The velocity of the runner ath the given time is 64.53 m/s

The distance travelled can be obtained as follow:

s = ut + ½at²

s = (7.5 × 53.3) + (½ × 1.07 × 53.3²)

s = 399.75 + (0.535 × 2840.98)

s = 399.75 + 1519.87615

s = 1919.63 m

Thus, the distance travelled in 53.3 seconds is 1919.63 m

v = u + at

v = 7.5 + (1.07 × 53.3)

v = 7.5 + 57.031

v = 64.53 m/s

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Answer:

10 m/s

Explanation:

Speed = wavelength * frequency

       =   5 m   *  2 / s   = 10 m/s

u = initial speed = 10 m/s

v = final speed = 14 m/s

Impulse is 2000 N/s

Given,

Mass of car = 500 kg

Force = 200 N

Acceleration = F/M

Acceleration = 0.4 m/s^2

Calculating the final speed,

u = initial speed = 10

v = final speed = ?

t = time of acceleration

v = u + at

v = 10 + (0.4 x 10)

v = 14m/s

Impulse = Ft = mv - uv

(200 x 10) = (500 x 14) - (500 x 10)

2000 = 7000 - 5000

2000 = 2000

Hence our answer is correct and the impulse is 2000 N/s.

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Answer:

Explanation:

Given:

m = 5.36 kg

h = 2.2 m

___________

A -?

Work:

A =m·g·h

A = 5.36·9.8·2.2 ≈ 116 J

A free body diagram of the box consists of weight of the box (50N) acting downwards, normal reaction acting upwards and applied force acting in x-direction.

A free-body diagram is a sketch of an object of interest with all the surrounding objects stripped away and all of the forces acting on the body shown.

The forces on the box;

The free body diagram of the forces acting on the box is illustrated as follows;

                                ↑ R

                      F    → Ф

                                ↓ W

Thus, a free body diagram of the box consists of weight of the box (50N) acting downwards, normal reaction acting upwards and applied force acting in x-direction.

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The maximum number of lamps that can be lighted at the same time without blow up of the fuse is 11.

The rate of performing labor is referred to as power. The amount of work (W) to the amount of time (T) is the ratio (t). Power(P)=Time(t) Work(W) In honor of physicist James Watt, the SI system of units uses the symbol W for power. Electric charge passes past a point in a circuit at a constant pace known as current. The rate at which an electric charge flows is defined as current. The potential difference in charge between two sites in an electrical field is known as voltage, also known as electromotive force.

Power= V*I

          =110 *5

          =550 watt

no. of lamps= 550/5

                   =11 lamps.

The maximum number of lamps that can be lighted at the same time without blow up of the fuse is 11.

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