Ask question

Ask question

All categories

2 years ago

12

A plant box falls from the windowsill 25.0 m above the sidewalk and hits the cement 3.0 s later. What is the box's velocity when

it hits the ground?
24 m/s
22 m/s
120 m/s

1 answer:

mamaluj [8]2 years ago

8 0

Answer:

22m/s

Explanation:

To find the velocity we employ the equation of free fall: v²=u²+2gh

where u is initial velocity, g is acceleration due to gravity h is the height, v is the velocity the moment it hits the ground, taking the direction towards gravity as positive.

Substituting for the values in the question we get:

v²=2×9.8m/s²×25m

v²=490m²/s²

v=22.14m/s which can be approximated to 22m/s

You might be interested in

D section a only still need help on this

SIZIF [17.4K]

Acceleration means speeding up, slowing down, or changing direction. The graph doesn't show anything about direction, so we just have to examine it for speeding up or slowing down ... any change of speed.

The y-axis of this graph IS speed. So the height of a point on the line is speed. If the line is going up or down, then speed is changing.

Sections a, c, and d are all going up or down. Section b is the only one where speed is not changing. So we can't be sure about b, because we don't know if the track may be curving ... the graph can't tell us that. But a, c, and d are DEFINITELY showing acceleration.

5 0

3 years ago

In February 2004, scientists at Purdue University used a highly sensitive technique to measure the mass of a vaccinia virus (the

OlgaM077 [116]

Answer:

a) m_v = m_s (( $\frac{w_o}{w}$ )² - 1) , b) m_v = 1.07 10⁻¹⁴ g

Explanation:

a) The angular velocity of a simple harmonic motion is

w² = k / m

where k is the spring constant and m is the mass of the oscillator

let's apply this expression to our case,

silicon only

w₉² = $\frac{K}{m_s}$

k = w₀² m_s

silicon with virus

w² = $\frac{k}{m_s + m_v}$

k = w² (m_v + m_s)

in the two expressions the constant k is the same and q as the one property of the silicon bar, let us equal

w₀² m_s = w² (m_v + m_s)

m_v = ( $\frac{w_o}{w}$ )² m_s - m_s

m_v = m_s (( $\frac{w_o}{w}$ )² - 1)

b) let's calculate

m_v = 2.13 10⁻¹⁶ [( $\frac{20.4}{2.85}$ )² - 1)]

m_v = 1.07 10⁻¹⁴ g

4 0

3 years ago

Compared to Earth's moon, the moons of Mars are

Mice21 [21]

I think is b I think

7 0

2 years ago

An ice sled powered by a rocket engine starts from rest on a large frozen lake and accelerates at 12.8 m/s2 . At t1 the rocket e

Simora [160]

Answer:4.39 s

Explanation:

Given

initial velocity $u=0$

acceleration $a=12.8 m/s^2$

velocity acquired by sled in $t_1$ time

$v=0+at$

$v=12.8t_1$

distance traveled by sled in $t_1 s$

$v^2-u^2=2as$

$(12.8t_1)^2-0=2\times 12.8\times s_1$

$s_1=6.4\cdot t_1^2$

distance traveled in $t_2$ time with velocity $v=12.8t_1$

$s_2=v\times t_2$

$s_2=12.8\times t_1\times t_2$

$s_2=12.8\cdot t_1\cdot t_2$

$s_1+s_2=5.37\times 10^3$

$6.4t_1^2+12.8t_1t_2=5370$ ----1

$t_1+t_2=97.7 s$

$t_2=97.7-t_1$

substitute the value of $t_2$ in 1

we get

$6.4t_1^2-1250.56t_1+5370=0$

thus $t_1=\frac{1250.56-1194.33}{12.8}=4.39 s$

$t_1=4.39 s$

5 0

3 years ago

A 0.3 g mosquito is flying toward a girl with a speed of 4.5 mph. Just before landing on the girl, the fly is swatted straight b

luda_lava [24]

Answer:

1.1x10^-2N

Explanation:

We have the change in momentum as

P = 0.3(4.5+12)g.mph

= 0.3x0.447x(4.5+12)x10^-3

Then the force that is exerted will be

F = p/∆t

∆t = 0.2

= 0.3x0.447x(4.5+12)x10^-3/0.2

= 0.1341x16.5x10^-3/0.2

= 1.1x10^-2

Therefore the force that was exerted is equal to 1.1x10^-2

5 0

2 years ago