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1 year ago

What do you mean by focus in science

1 answer:

4 0

“a point at which rays of light, heat, or other radiation meet after being refracted or reflected.” Meaning multiple light rays or heat (and other forms of radiation) are all being refracted or reflecting to a certain point

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A 200 kg weather rocket is loaded with 100 kg of fuel and fired straight up. It accelerates upward at 30 m/s2 for 35 s , then ru

Gre4nikov [31]

Answer:

a) $h_m=74625\ m$

b) $t=265.55\ s$

Explanation:

Given:

mass of rocket, $m_r=200\ kg$

mass of fuel, $m_f=100\ kg$

acceleration of the rocket consuming fuel, $a=30\ m.s^{-2}$

time after which the fuel exhaust, $t_f=35\ s$

During the phase of fuel exhaustion:

velocity attained by the rocket just as the fuel ends:

$v_f=u+a.t_f$

where:

$u=$ initial velocity of the rocket = 0

$v_f=0+30\times 35$

$v_f=1050\ m.s^{-1}$ this will be the initial velocity for the phase of ascending of the rocket's height under the influence of gravity.

height at which the fuel finishes:

$v_f^2=u^2+2a.h_f$

$1050^2=0^2+2\times 30\times h_f$

$h_f=18375\ m$

During the phase of ascend in height of rocket after the fuel is over:

Time taken to reach the top height after the fuel is over:

$v=v_f+g.t'$

at top v = (final velocity during this course of motion )= 0 $m.s^{-1}$

$0=1050-9.8\times t'$

$t'=107.1429\ s$

Height ascended by the rocket after the fuel is over:

$v^2=v_f^2+2g.h'$

at the top height the velocity is zero

$0^2=1050^2-2\times 9.8\times h'$ (-ve sign denotes that the direction of motion is opposite to that of acceleration)

$h'=56250\ m$

Therefore the maximum altitude attained by the rocket:

$h_m=h_f+h'$

$h_m=18375+56250$

$h_m=74625\ m$

time taken by the rocket to fall back to the earth:

$h_m=v.t_m+\frac{1}{2} g.t_m^2$

where:

$v=$ initial velocity of the rocket during the course of free fall from the top height.

$74625=0+4.9\times t_m^2$

$t_m=123.41\ s$

Now the total time for which the rocket is in the air:

$t=t_f+t'+t_m$

$t=35+107.1429+123.41$

$t=265.55\ s$

4 0

3 years ago

A. How can a spinning ball have more lift than one that is not spinning?

sergiy2304 [10]

Answer:

It is spinning, making the ball a little more airborn than the one that isn't spinning

6 0

3 years ago

a 1020-hertz sound wave travels at 340 m/s in air with a wavelength of a) 30 m. b) 3 m. c) 0.333 m. d) 1 m. e) none of the above

eimsori [14]

The wavelength of the sound wave is equal to 0.333 m. Therefore, option (c) is correct.

<h3>What are frequency and wavelength?</h3>

The frequency of the wave can be defined as the number of oscillations that occur in one second and can be expressed in hertz. The wavelength can be defined as the distance between the two adjacent points of a wave such as two crests or troughs.

The relationship between frequency (ν), speed of sound waves (V), and wavelength (λ):

V = νλ

Given, the frequency of the sound wave, ν = 10 Hz

The speed of the sound wave, $V = 340 m/s$