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zlopas [31]
3 years ago
8

A soccer ball is sitting in the middle of a soccer field during a game. When the referee blows his whistle, one of the players r

uns toward the ball and kicks it as hard as he can. The ball flies toward the other team's goal at a rate of about 55 miles per hour.
At what rate is the ball moving just before the player kicks it?
Physics
2 answers:
NikAS [45]3 years ago
6 0
Before its moving it should be 0 right 
valkas [14]3 years ago
5 0

Answer:

0

Explanation:

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A block of mass m=16.8 kg is sliding on a surface with initial velocity v=23.2 m/s. The block has a coefficient of kinetic frict
Firdavs [7]

Answer:

t = 23.92 s

Explanation:

Newton's second law:

∑F = m*a Formula (1)

∑F : algebraic sum of the forces in Newton (N)

m : mass s (kg)

a : acceleration  (m/s²)

We define the x-axis in the direction parallel to the movement of the block  and the y-axis in the direction perpendicular to it.

Forces acting on the block

W: Weight of the block : In vertical direction, downward

FN : Normal force : perpendicular to the floor, upward

fk :  Kinetic friction force: parallel to the floor  and opposite to the movement

F = 86.4 N , in the direction of the motion

Calculated of the W

W= m*g

W=  16.8 kg* 9.8 m/s² = 164.64 N

Calculated of the FN  

We apply the formula (1)  

∑Fy = m*ay ay = 0  

FN - W = 0  

FN = W  

FN =  164.64 N

Calculated of the fk

fk  = μk*FN

fk  = 0.426* 164.64 N

fk  = 70.13 N

We apply the formula (1) to calculated acceleration of the block:

∑Fx = m*ax  ,  ax= a  : acceleration of the block

F - fk = m*a

86.4 -70.13  = (16.8)*(-a)

16.26 =  (16.8)*(-a)

a = -(16.26 )/ (16.8)

a = - 0.97 m/s²

Kinematics of the block

Because the block moves with uniformly accelerated movement we apply the following formula :

vf = v₀ + a*t   Formula (2)

Where:  

t: time interval  (m)

v₀: initial speed  (m/s)

vf: final speed   (m/s)

Data:

v₀ = 23.2 m/s

vf = 0

a =  -0.97 m/s²  

Time it takes for the block to stop

We replace data in the formula (2)  to calculate the time

vf= v₀+a*t

0 = 23.2+( -0.97)*t

(0.97)*t  = 23.2

(0.97)*t  = 23.2

t = 23.2 / (0.97)

t = 23.92 s

7 0
3 years ago
What caused rutherford to propose a revised model of the atom
Wewaii [24]

Explanation:

Rutherford proposed a revised model for the atom, called the planetary model. The previous model of the atom was Thomson's Plum Pudding Model which consisted of freely moving positive and negative charges inside the atom.

Rutherford proposed his model after an experiment he conducted called the Gold Foil Experiment. This experiment consisted of a thin gold sheet into which alpha particles were shot upon and they were detected by a sensor. The image attached will give a better explanation of this. In this experiment he shot a beam of alpha particles(helium nucleus) at a thin sheet of gold. Rutherford hypothesised that there should be minimum deflection of the positively charged alpha particles occuring due to the repulsion of the alpha particle with the positive charges in the thin gold sheet. This was not the case.

However what he found was that most of alpha particles went straight through the thin sheet of gold but some were reflected back to him. This surprised him. Hence he proposed that most of the atom must be empty space as most of the alpha particles went straight through the sheet and there must be a heavy nucleus inside the atom causing the alpha particles to bounce back.

7 0
3 years ago
Plz, Help I just need this question to be answered so I can be done with this worksheet.
Neko [114]

Answer:

2 if I'm not wrong.

I hope it will be useful.

3 0
3 years ago
Fiber is an example of a complex carbohydrate true or false
kkurt [141]
The answer is True
Fiber is an example
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3 years ago
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If your Stronger than Hisoka, and you know it, Clap your hands! Oh, wait.. That’s right! You don’t have any hands. Lol
ddd [48]

Answer:

Haha pretty funny

Explanation:

3 0
2 years ago
Read 2 more answers
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