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Oliga [24]
3 years ago
9

To practice Tactics Box 9.1 Calculating the Work Done by a Constant Force. Recall that the work W done by a constant force F⃗ at

an angle θ to the displacement Δr⃗ is W=F⃗ ⋅ Δr⃗ =FΔrcosθ. The vector magnitudes F and Δr are always positive, so the sign of W is determined entirely by the angle θ between the force and the displacement.
Physics
2 answers:
garri49 [273]3 years ago
4 0

Answer:

See espplanation below.

Explanation:

The deduction of the formula given is this one:

We can assume that we have a constant force F acting on a point that follows a curve Y with a velocity v at each instant, we can define an small amount of work d W who occurs on a instant dt and we can calculate it as:

d W= F dr = F v dt

And we have that Fv represent the power at the instant dt and we can sum all the small amounts for the work in the entire trajectory with the following integral:

W =\int_{t_1}^{t_2} F v dt = \int_{t_1}^{t_2} F \frac{dr}{dt} dt =\int_M F ds

And M represent the trajectory from y(t_1) to y(t_2)

If we assume that the force is constant so then we can do this with the integral:

W= \int_M F dr = F \int_M dr = F \Delta r

Where \Delta r represent the displacement of the point along the curve.

We know that the fot product can be expressed on this way:

F \Delta r = f Cos \theta dr

Where \theta represent the angle between the force vector and the direction of the movement, so in general we have this:

W= \int_M F dr = F \Delta r cos \theta

And as we can see F and \Delta r are scalars (assumed constant both) and not affect the sign of the work, so the only value that affect the sign of W is the angle since depedens of the cosine function who is maximum at 0 and 2\pi and minimum at \pi/2

insens350 [35]3 years ago
3 0

Answer:

The vector magnitudes F and r are always postive, so the sign o W is determined entirely by the angle e between the force and the displacement.Submit Figure 1 off 1 part C

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Feliz [49]

a. 46 m/s east

The jet here is moving with a uniform accelerated motion, so we can use the following suvat equation to find its velocity:

v=u+at

where

v is the velocity calculated at time t

u is the initial velocity

a is the acceleration

The jet in the problem has, taking east as positive direction:

u = +16 m/s  is the initial velocity

a=+3 m/s^2  is the acceleration

Substituting t = 10 s, we find the final velocity of the jet:

v=16 + (3)(10)=46 m/s

And since the result is positive, the direction is east.

b. 310 m

The displacement of the jet can be found using another suvat equation

s=ut+\frac{1}{2}at^2

where

s is the displacement

u is the initial velocity

a is the acceleration

t is the time

For the jet in this problem,

u = +16 m/s  is the initial velocity

a=+3 m/s^2  is the acceleration

t = 10 s is the time

Substituting into the equation,

s=(16)(10)+\frac{1}{2}(3)(10)^2=310 m

4 0
3 years ago
A body weighs 10newton in air and 9.5 in water. How will it weigh in alchohol if density 0.8gcm-³​
Katen [24]

Answer:

The weight of object in alcohol is, W₀ = 9.6 N

Explanation:

Given,

The weight of body in air, Wₐ = 10 N

The weight of the body in water, Wₓ = 9.5 N

The density of the alcohol, ρ = 0.8 g/cm³

                                                = 800 kg/m³

The weight of body in water = weight of object in air - weight of water displaced

                        9.5 N = 10 N - weight of water displaced

                       Weight of water displaced = 0.5 N

The mass of the displaced water, m = 0.5 / 9.8

                                                            = 0.051 kg

Therefore the volume of the water displaced,

                                              V = m / ρ

                                                  = 0.051 / 1000

                                                   = 5.1 x 10⁻⁵ m³

<em>The volume of water displaced is equal to the volume of alcohol displaced</em>

Therefore, the mass of the alcohol displaced, = V x ρ

                                                                             = 5.1 x 10⁻⁵ x 800

                                                                             = 0.0405 kg

The weight of the alcohol displaced, w = 0.0405 x 9.8

                                                                    = 0.4 N

Therefore,

The weight of body in alcohol = weight of object in air - weight of alcohol displaced

                             W₀ = W - w

                                    = 10 N - 0.4 N

                                     = 9.6 N

Hence, the weight of object in alcohol is, W₀ = 9.6 N

4 0
3 years ago
The distance between adjacent nodes in a standing wave pattern in a length of string is 25.0 cm:A. What is the wavelength of wav
mina [271]

A) 50 cm

B) 10000 cm/s

Explanation

Step 1

A)

If you know the distance between nodes and antinodes then use this equation:

\begin{gathered} \frac{\lambda}{2}=D \\ \text{where}\lambda\text{ is the wavelength} \\ D\text{ is the distance betw}een\text{ nodes} \end{gathered}

then, let

D=\text{ 25 cm }

now, replace to find the wavelength

\begin{gathered} \frac{\lambda}{2}=25 \\ \text{Multiply both sides by 2} \\ \frac{\lambda}{2}\cdot2=25\cdot2 \\ \lambda=50\text{ Cm} \end{gathered}

so, the wavelength is

A) 50 cm

Step 2

The speed of a wave can be found using the equation

v=\lambda f

or velocity = wavelength x frequency,

then,let

\begin{gathered} \lambda=50\text{ cm} \\ f=200\text{ Hz} \end{gathered}

replace and evaluate

\begin{gathered} v=\lambda f \\ v=50\text{ cm }\cdot200\text{ HZ} \\ v=10000\text{ }\frac{\text{cm}}{s} \end{gathered}

so

B) 10000 cm/s

I hope this helps you

6 0
1 year ago
How do the processes of weathering, erosion, and deposition affect the ecoregions of Texas? Give a specific example of how each
NISA [10]

Answer:

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5 0
3 years ago
Nuclear energy is over ___ times stronger than the chemical bonds between the atoms
Kamila [148]

Answer:

1 millions times stronger

8 0
2 years ago
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