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d1i1m1o1n [39]
3 years ago
14

Can someone help me ​

Physics
2 answers:
Julli [10]3 years ago
6 0
The answer is the first one
arsen [322]3 years ago
3 0

Answer:

C?

Explanation:

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A train travels 90 kilometers in 2 hours, and then 66 kilometers in 2 hours. What is its average speed?
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90+66=156
156/2=78

Reply:78kilometers in 2 hours.
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3 years ago
A child throws a baseball upward with an initial velocity of 20 m/s. The child wants to throw the baseball at least as high as t
Umnica [9.8K]
When the ball starts its motion from the ground, its potential energy is zero, so all its mechanical energy is kinetic energy of the motion:
E= \frac{1}{2}mv^2
where m is the ball's mass and v its initial velocity, 20 m/s.

When the ball reaches its maximum height, h, its velocity is zero, so its mechanical energy is just gravitational potential energy:
E=mgh

for the law of conservation of energy, the initial mechanical energy must be equal to the final mechanical energy, so we have
\frac{1}{2}mv^2 = mgh
From which we find the maximum height of the ball:
h= \frac{v^2}{2g}= \frac{(20 m/s)^2}{2 \cdot 9.81 m/s^2}=20.4 m

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5 0
3 years ago
An example of acceleration
TEA [102]

Answer:

Explanation:

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3 years ago
A 4.80 −kg ball is dropped from a height of 15.0 m above one end of a uniform bar that pivots at its center. The bar has mass 7.
Margarita [4]

Answer:

h = 13.3 m

Explanation:

Given:-

- The mass of ball, mb = 4.80 kg

- The mass of bar, ml = 7.0 kg

- The height from which ball dropped, H = 15.0 m

- The length of bar, L = 6.0 m

- The mass at other end of bar, mo = 5.10 kg

Find:-

The dropped ball sticks to the bar after the collision.How high will the other ball go after the collision?

Solution:-

- Consider the three masses ( 2 balls and bar ) as a system. There are no extra unbalanced forces acting on this system. We can isolate the system and apply the principle of conservation of angular momentum. The axis at the center of the bar:

- The angular momentum for ball dropped before collision ( M1 ):

                                 M1 = mb*vb*(L/2)

Where, vb is the speed of the ball on impact:

- The speed of the ball at the point of collision can be determined by using the principle of conservation of energy:

                                  ΔP.E = ΔK.E

                                  mb*g*H = 0.5*mb*vb^2

                                  vb = √2*g*H

                                  vb = ( 2*9.81*15 ) ^0.5

                                  vb = 17.15517 m/s

- The angular momentum of system before collision is:

                                  M1 = ( 4.80 ) * ( 17.15517 ) * ( 6/2)

                                  M1 = 247.034448 kgm^2 /s

- After collision, the momentum is transferred to the other ball. The momentum after collision is:

                                  M2 = mo*vo*(L/2)

- From principle of conservation of angular momentum the initial and final angular momentum remains the same.

                                 M1 = M2

                                 vo = 247.03448 / (5.10*3)

                                 vo = 16.14604 m/s

- The speed of the other ball after collision is (vo), the maximum height can be determined by using the principle of conservation of energy:

                                  ΔP.E = ΔK.E

                                  mo*g*h = 0.5*mo*vo^2

                                  h = vo^2 / 2*g

                                  h = 16.14604^2 / 2*(9.81)

                                  h = 13.3 m

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3 years ago
What can we say about microwaves<br> waves on the electromagnetic spectrum?
Elena L [17]

Answer:

Microwaves fall in the range of the EM spectrum between radio and infrared light.

Explanation:

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