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3 years ago

How significant is air resistance for projectile motion?

Physics

1 answer:

miv72 [106K]3 years ago

8 0

Answer:

Air resistance have some significant role in projectile motion if the motion lasts for some time.

Explanation:

Air resistance or air drag seems to be important in daily actvities and games like baseball.

The trajectory of the projectile with or without air resistance or air drag is totally different.

When we neglect air drag, the only acting force is gravity against the motion so the maximum height and range are suppose Hmax and R.

Now, when we consider air drag, it is important to notice that there are two forces against the motion of the ball and along the direction of gravity. It seems that both maximum height and range are lesser Hmax'< Hmax and R'<R.

You might be interested in

Match the indices of refraction with the corresponding effects on the waves.

Yanka [14]

Answer:

B) waves speed up

C) waves bend away from the normal

Explanation:

The index of refraction of a material is the ratio between the speed of light in a vacuum and the speed of light in that medium:

$n=\frac{c}{v}$

where

c is the speed of light in a vacuum

v is the speed of light in the medium

We can re-arrange this equation as:

$v=\frac{c}{n}$

So from this we already see that if the index of refraction is lower, the speed of light in the medium will be higher, so one correct option is

B) waves speed up

Moreover, when light enters a medium bends according to Snell's Law:

$n_1 sin \theta_1 = n_2 sin \theta_2$

where

$n_1 ,n_2$ are the index of refraction of the 1st and 2nd medium

$\theta_1,\theta_2$ are the angles made by the incident ray and refracted ray with the normal to the interface

We can rewrite the equation as

$sin \theta_2 = \frac{n_1}{n_2}sin \theta_1$

So we see that if the index of refraction of the second medium is lower ( $n_2$ ), then the ratio $\frac{n_1}{n_2}$ is larger than 1, so the angle of refraction is larger than the angle of incidence:

$\theta_2>\theta_1$

This means that the wave will bend away from the normal. So the other correct option is

C) waves bend away from the normal

3 0

3 years ago

An iron railroad rail is 700 ft long when the temperature is 30°C. What is its length when the temperature is – 10°C?

MAVERICK [17]

Answer:

699.67ft

Explanation:

We are given with,

α = 1.2×10⁻⁵ / °C
L₀ = 700 ft
ΔT = -10°C − 30°C = -40°C

Now, We have to find ΔL:

ΔL = (1.2×10⁻⁵ / °C) (700 ft) (-40°C)
ΔL = −0.336

Rounded to two significant figures, the change in length is −0.33ft.

<u>Therefore, the final length is approximately 700 ft − 0.33 ft = 699.67ft</u>.

6 0

3 years ago

Sarah weighs 500 newtons. She climbs a set of stairs 6 meters high. How much work does she do? 83 J Work equals force times dist

jek_recluse [69]

Answer:

<em>Answer: Work equals force times distance. 3,000 J</em>

Explanation:

Work Done By A Force

When some force $\vec F$ is applied and a displacement $\vec r$ is achieved, the work done by the force is given by

$W=\vec F \cdot \vec r$

Note that the work is a scalar magnitude as the result of the dot-product of two vectors. If the force and the displacement are parallel, then the vectors can be replaced as its magnitudes F,x and the work is

$W=F.x$

The dot product becomes a simple arithmetic product, i.e force times distance.

Sara weighs 500 Nw and she climbs up a 6 meter set of stairs. She needs to lift her weight up, so the force is the weight and the distance is the height of the stairs, thus

$W=500\ Nw.\ 6\ m=3,000\ Joule$