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4 years ago

13

Important changes in the musculoskeletal system due to physical activity seem to begin at _______ minutes of activity a week. A.

30 B. 60 C. 80 D. 90

1 answer:

baherus [9]4 years ago

5 0

I think the answer is a

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Suppose that a car traveling to the west (-x direction) begins to slow down as it approaches a traffic light. Make a statement c

nata0808 [166]

Answer:

The car is decelerating and its acceleration is negative.

Explanation:

First thing to consider. The car traveling direction is not important to answer the question.

Second, there are two affirmations on each sentence. So, lets take definitions:

Deceleration: Reducing the acceleration, from one value to another. No matter if the acceleration for the moment is positive or negative.

Acceleration negative: the driver is applying a force to make speed=0, the sign of this force must negative in order for the car to stop, other way it will go faster. Acceleration is the change rate of speed, if the speed is going down, the total acceleration until cars stops must be negative.

4 0

3 years ago

When hydrogen is heated or subjected to an electric discharge, it emits light with specific visible wavelengths. A diffraction g

BartSMP [9]

To solve this problem we will apply the concepts related to the double slit-experiment. For which we will relate the distance between the Slits and the Diffraction Angle with the order of the bright fringe and the wavelength, this is mathematically given as,

$d sin\theta = m\lambda$

Here,

d = Distance between Slits

m = Order of the fringes

$\lambda$ = Wavelength

$\text{Spacing between adjacent lines}$ = $d = 4926nm$

$\text{Wavelength of light} = \lambda = 656nm$

Rearranging to find the angle,

$sin\theta = \frac{m\lambda}{d}$

$\theta = sin^{-1}(\frac{m\lambda}{d})$

$\theta = sin^{-1}(\frac{(4)(656*10^{-9}m)}{4926*10^{-9}m})$

$\theta = 32.19\°$

Therefore the angle that the fourth order bright fringe occur for this specific wavelenth of light occur is 32.19°

3 0

3 years ago

Plates move apart at ____ boundaries.

Keith_Richards [23]

<span>The correct answer is C. divergent. Divergent boundaries are something like lines found between two tectonic plates. These constructive boundaries, or extensional boundaries, are formed and exist between two tectonic plates that move away from each other. Convergent would thus be where they meet. This is all according to the tectonic theory.</span>

5 0

3 years ago

Read 2 more answers

A student says that a speed of 50 m/s is faster than a speed of 140 km/h because the number is bigger. What would you say to the

denis23 [38]

Yes you are right but sometimes just because a number is bigger doesnt always make it so.

5 0

3 years ago

Electrons in a particle beam each have a kinetic energy of 4.0 × 10−17 J. What is the magnitude of the electric field that will

denpristay [2]

Explanation:

Relation between work and change in kinetic energy is as follows.

$W_{net} = \Delta K$

Also, $\Delta K = K_{initial} - K_{final}$

= $(0 - 4.0 \times 10^{-17})$ J

= $-4.0 \times 10^{-17}$ J

Let us assume that electric force on the electron has a magnitude F. The electron moves at a distance of 0.3 m opposite to the direction of the force so that work done is as follows.

w = -Fd

$-4.0 \times 10^{-17} J = -F \times 0.3 m$

F = $1.33 \times 10^{-16}$

Therefore, relation between electric field and force is as follows.

E = $\frac{F}{q}$

= $\frac{1.33 \times 10^{-16}}{1.60 \times 10^{-19} C}$

= $0.831 \times 10^{3}$ C

Thus, we can conclude that magnitude of the electric field that will stop these electrons in a distance of 0.3 m is $0.831 \times 10^{3}$ C.

3 0

3 years ago