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padilas [110]
3 years ago
5

Which muscles help you sit up from laying down?​

Physics
2 answers:
harkovskaia [24]3 years ago
6 0
Abdominal muscles I think
rosijanka [135]3 years ago
3 0

Answer: abdominal muscles.

Explanation:

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A box of mass 50 kg is pushed hard enough to set it in motion across a flat surface. Then a 99-N pushing force is needed to keep
salantis [7]
The box is kept in motion at constant velocity by a force of F=99 N. Constant velocity means there is no acceleration, so the resultant of the forces acting on the box is zero. Apart from the force F pushing the box, there is only another force acting on it in the horizontal direction: the frictional force F_f which acts in the opposite direction of the motion, so in the opposite direction of F.
Therefore, since the resultant of the two forces must be zero,
F-F_f=0
so
F=F_f

The frictional force can be rewritten as
F_f = \mu m g
where m=50 kg, g=9.81 m/s^2. Re-arranging, we can solve this equation to find \mu, the coefficient of dynamic friction:
\mu =  \frac{F}{mg}= \frac{99 N}{(50 kg)(9.81 m/s^2)}  =0.20
4 0
3 years ago
A ball is thrown eastward into the air from the origin (in the direction of the positive x-axis). The initial velocity is 50 i +
nikklg [1K]

Answer:

The ball lands 154.3 ft from the origin at an angle of 13.6° from the eastern direction toward the south.

Explanation:

Hi there!

The position vector of the ball is described by the following equation:

r = (x0 + v0x · t + 1/2 · ax · t², y0 + v0y · t + 1/2 · ay · t², z0 + v0z · t + 1/2 · g · t²)

Where:

r =  poisition vector of the ball at time t.

x0 = initial horizontal position.

v0x = initial horizontal velocity (eastward).

t = time.

ax = horizontal acceleration (eastward).

y0 = initial horizontal position.

v0y = initial horizontal velocity (southward).

ay = horizontal acceleration (southward)

z0 = initial vertical position.

v0z = initial vertical velocity.

g = acceleration due to gravity.

We have to find at which time the vertical component of the position vector is zero (the ball is on the ground) and then we can calculate the horizontal distance traveled by the ball at that time, using the equations of the horizontal components of the position vector.

Let´s place the origin of the system of reference at the throwing point so that x0 and y0 and z0 = 0.

y =  z0 + v0z · t + 1/2 · g · t²            (z0 = 0)

0 = 48 ft/s · t - 1/2 · 32 ft/s² · t²

0 = t (48 ft/s - 16 ft / s² · t)                 (t= 0, the origin point)

0 = 48 ft/s - 16 ft / s² · t

- 48 ft/s / -16 f/s² = t

t = 3.0 s

Now, we can calculate how much distance the ball traveled in that time.

First, let´s calculate the distance traveled in the eastward direction:

x = x0 + v0x · t + 1/2 · ax · t²              (x0 = 0, ax = 0 there is no eastward acceleration)

x = 50 ft/s · 3 s

x = 150 ft

And now let´s calculate the distance traveled in southward direction:

y = y0 + v0y · t + 1/2 · ay · t²   (y0 = 0 and v0y = 0, initially, the ball does not have a southward velocity).

y =  1/2 · ay · t²

y = 1/2 · (-8 ft/s²) · (3 s)²

y = -36 ft

Then, the final position vector will be:

r = (150 ft, -36 ft, 0)

The traveled distance is the magnitude of the position vector:

|r| = \sqrt{(150ft)^{2} + (-36ft)^{2}} = 154.3 ft

To calculate the angle, we have to use trigonometry (see attached figure):

cos angle  = adjacent side / hypotenuse

cos α = x/r

cos α = 150 ft / 154.3 ft

α = 13.6°

The ball lands 154.3 ft from the origin at an angle of 13.5° from the eastern direction toward the south.

8 0
3 years ago
Two atoms that are isotopes will have a different number of what​
BigorU [14]

Answer:

different number of mass numbers.

Explanation:

isotopes are atoms of the same element having the same atomic number but different mass numbers due to different number of neutrons.

7 0
3 years ago
Why is physics important for high school students to learn?
Bond [772]

It is important for people to learn physics so that they can better understand the basic laws of the universe, and most importantly, so we can look at things with common sense, for you my friend i recommend watching <em>mythbusters</em>, they teach physics and make learning fun they teach you to look at the world with common sense. hope i helped!!! have a good day.


7 0
4 years ago
Nicole built a parachute, as seen here. She dropped the parachute from the top of the stairs, and it floated down very quickly.
siniylev [52]

answer C

Explanation:

5 0
2 years ago
Read 2 more answers
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