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2 years ago

When a skateboarder rides down a hill, the normal force exerted on the skater by the hill is

Physics

1 answer:

Luda [366]2 years ago

3 0

Newton's second law allows us to find that the correct answer is:

Less than weight of the skater

Newton's second law states that the net force and is propositional to the mass and acceleration of the body

For these problems it is essential to set a reference system, with respect to which to carry out the measurements, in this case we set a coordinate system with the x axis parallel to the plane and positive in the direction of movement and the y axis perpendicular to the plane.

In the attachment we can see a free-body diagram of the problem, let's work each axis separately

x-axis

Wₓ -fr = m a

y-axis

N - $W_y$ = 0

N = $W_y$

Where Wₓ and W_y are the components of the weight, fr the friction force that opposes the movement, m the mass and the acceleration of the body

let's use trigonometry to find the components of the weight

cos θ = $\frac{W_y}{W}$

sin θ = $\frac{W_x}{W}$

$W_y$ = W cos θ

Wₓ = W sin θ

we substitute

N = mg cos θ

From this equation we can see that the normal is less than the weight of the body.

In conclusion using Newton's second law we find that the correct answer is:

Less than th weight of the skater

Learn more about Newton's second law here:

brainly.com/question/13685393

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A marathon runner completes a 42.238 km course in 2 h, 31 min, and 46 s . There is an uncertainty of 29 m in the distance run an

icang [17]

Answer:

The percentage uncertainty in the average speed is 0.10% (2 sig. fig.)

Explanation:

Consider the formula for average speed $\bar{v}$ .

$\displaystyle \bar{v} = \frac{s}{t}$ ,

where

$s$ is the total distance, and
$t$ is the time taken.

The percentage uncertainty of a fraction is the sum of percentage uncertainties in

the numerator, and
the denominator.

What are the percentage uncertainties in $s$ and $t$ in this question?

The unit of the absolute uncertainty in $s$ is meters. Thus, convert the unit of $s$ to meters:

$s = \rm 42.238\;km = 42.238\times 10^{3}\;m$ .

$\begin{aligned}\displaystyle \text{Percentage Uncertainty in }s &= \frac{\text{Absolute Uncertainty in } s}{\text{Measured Value of }s}\times 100\% \\ &=\rm\frac{29\; m}{42.238\times 10^{3}\;m}\times 100\%\\ &= 0.0687\%\end{aligned}$ .

The unit of the absolute uncertainty in $t$ is seconds. Convert the unit of $t$ to seconds:

$t = \rm 2\times 3600 + 31\times 60 + 46 = 9106\;s$

Similarly,

$\begin{aligned}\displaystyle \rm \text{Percentage Uncertainty in }t &= \frac{\text{Absolute Uncertainty in }t}{\text{Measured Value of }t}\times 100\% \\ &=\rm\frac{46\; s}{9106\;s}\times 100\%\\ &= 0.0329\%\end{aligned}$ .

The average speed $\bar{v}$ here is a fraction of $s$ and $t$ . Both $s$ and $t$ come with uncertainty. The percentage uncertainty in $\bar{v}$ will be the sum of percentage uncertainties in $s$ and $t$ . That is:

$\text{Percentage Uncertainty in }\bar{v}\\=(\text{Percentage Uncertainty in } s) + (\text{Percentage Uncertainty in } t)\\ = 0.0687\% + 0.0329\%\\ = 0.010\%$ .

Generally, keep

two significant figures for percentage uncertainties that are less than 2%, and
one for those that are greater than 2%.

The percentage uncertainty in $\bar{v}$ here is less than 2%. Thus, keep two significant figures. However, keep more significant figures than that in calculations to make sure that the final result is accurate.

3 0

4 years ago

An alternating-current (AC) source supplies a sinusoidally varying voltage that can be described with the function v of t is equ

Marrrta [24]

Answer:

ω, the angular frequency of the source equals 377 rad/s

Explanation:

From the question, V(t) = V cosωt.

Now, ω = the angular frequency of the sinusoidal wave is given by

ω = 2πf where f = the frequency of the source = 60 Hz

So, the angular frequency of the source ,ω = 2π × the frequency of the source.

So, ω = 2πf

ω = 2π × 60 Hz

ω = 120π rad/s

ω = 376.99 rad/s

ω ≅ 377 rad/s

So, ω, the angular frequency of the source equals 377 rad/s

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3 years ago

Infants will often smile when they hear a parent's voice. In this situation, the parents voice is considered

Ugo [173]

Soothing? I don't really know are there any choices?

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4 years ago

Read 2 more answers

If net force is zero, the what will be constant.

vodomira [7]

Answer:

The ans is velocity

Explanation:

Hope it helps you

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3 years ago

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Runoffs from an uranium mine stockpile have contaminated the surface water in a location. This might cause health problems among

xz_007 [3.2K]

The best plan to solve the problem of health problems among people, because of the contaminated surface water is to collect the runoffs in retention ponds for isolation and recovery of contaminants. Correct answer: D

This is tn eonly option from the given that is the most efficient and prodcutive way to solve this problem.

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3 years ago