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3 years ago

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A person running down the hallway at a velocity of 4.2 m/s comes to a stop in a time of 1.8 seconds to avoid hitting the wall. W

hat was the acceleration of the person?
A.) 7.6 m/s/s
B.) -7.6 m/s/s
C.) 2.3 m/s/s
D.) -2.3 m/s/s

2 answers:

kumpel [21]3 years ago

6 0

Hshshshhshdhdhdhdhddhdhdhdhdhdh

adoni [48]3 years ago

3 0

Answer:

It's not -7.6

Explanation:

All I can tell you

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A box slides down a frictionless ramp.if it starts at rest, what is it’s speed at the bottom?

zhenek [66]

8.854 m/s is the speed of the box after it reaches bottom of the ramp.

<u>Explanation</u>:

From the figure we came to know that height of the block is 4 m.

We know that,

Total "initial energy of an object" = Total "final energy of an object "

Total "initial energy of an object" is = "sum of potential energy" and "kinetic energy" of an object at its initial position.

$\text { "g" acceleration due to gravity is } 9.8 \mathrm{m} / \mathrm{s}^{2}$

$\text { Total initial energy }=\mathrm{m} \times \mathrm{g} \times \mathrm{h}_{\mathrm{i}}+\frac{1}{2} \mathrm{m} v_{i}^{2}$

Initial velocity is “0” as the object does not have starting speed

$\text { Height of the block where the object is placed initially }\left(h_{i}\right) \text { is } 4 \mathrm{m} \text { . }$

$\text { Total initial energy }=\mathrm{m} \times 9.8 \times 4+\frac{1}{2} \mathrm{m} 0^{2}$

Total initial energy = 39.2 × m

$\text { Total final energy }=\mathrm{m} \times \mathrm{g} \times \mathrm{h}_{\mathrm{f}}+\frac{1}{2} m v_{f}^{2}$

$\text { We need to find final velocity } v_f$

$\text { Height of the block where the object is travelled to bottom (h_) is } 0 \mathrm{m} \text { . }$

$\text { Total final energy }=\mathrm{m} \times 9.8 \times 0+\frac{1}{2} m v_{f}^{2}$

Now, Total initial energy of an object = Total final energy of an object

$39.2 \times \mathrm{m}=0.5 \mathrm{m} v_{f}^{2}$

$\frac{39.2}{0.5}=v_{f}^{2}$

$v_{f}^{2}=78.4$

$v_{f}=\sqrt{78.4}$

$v_{f}=8.854 \mathrm{m} / \mathrm{s}$

Final speed is 8.854 m/s.

3 0

3 years ago

Two forces of magnitudes 4.0 Newtons and 3.0 Newtons pull on a box. The forces make an angle of 40° with each other. What is the

leonid [27]

Answer:

6.6 N

Explanation:

Let's take the direction of the force of 4.0 N as positive x-direction. This means that the force of 3.0 N is at 40 degrees above it. So the components of the two forces along the x- and y-directions are:

$F_{1x} = 4.0 N\\F_{1y} = 0$

$F_{2x} = 3.0 N cos 40^{\circ}=2.3 N\\F_{2y} = 3.0 N sin 40^{\circ} = 1.9 N$

So the resultant has components

$F_x = F_{1x}+F_{2x}=4.0 N +2.3 N = 6.3 N\\F_y = F_{1y} + F_{2y} = 0 + 1.9 N = 1.9 N$

So the magnitude of the resultant is

$F=\sqrt{F_x^2 +F_y^2}=\sqrt{(6.3)^2+(1.9)^2}=6.6 N$

And in order for the body to be balanced, the third force must be equal and opposite (in direction) to this force: so, the magnitude of the third force must be 6.6 N.

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3 years ago

Help me please. I’ll select brainliest!

pishuonlain [190]

Answer:

90 degrees

Explanation:

the answer is 90 because angle a has a square on the angle which means it is 90 degrees

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Gwar [14]

The one that will change the velocity of a periodic wave is :
B. Changing the medium of the wave
Waves is always determined by the properties of the medium, which means that changing the medium will change the velocity of the wave

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3 years ago

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