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3 years ago

Physics pls help

Physics

2 answers:

seropon [69]3 years ago

3 0

First one is correct

WARRIOR [948]3 years ago

3 0

Answer: -0.33m/s (A)

Explanation:

According to the law of conservation of momentum, the sum of momentum before collision is equal to sum of their momentum after collision. They move with the same velocity (v) after collision.

Momentum = mass × velocity

For 4kg mass with velocity of 3m/s,

Its momentum = 4×3 = 12kgm/s

For 8kg mass with velocity of 2m/s,

Its momentum = 8 × -2 = -16kgm/s.

The velocity of 8kg mass is negative because it is moving towards the left(-ve x-direction).

Sum of momentum before collision = 12+(-16) = -4kgm/s... (1)

Momentum of 4kg body after collision = 4v

Momentum of 8kg body after collision = 8v

Sum of momentum after collision = 4v+8v = 12v...(2)

Equating 1 and 2 according to law of conservation of momentum, we have;

-4 = 12v

V = -4/12

V = -0.33m/s

Therefore their velocity after collision is -0.33m/s

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An electromagnetic wave is transporting energy in the negative y direction. At one point and one instant the magnetic field is i

natali 33 [55]

Answer:. Option c

Explanation: the speed of an electromagnetic wave is simply the vector product of the magnetic field and the electric field.

The direction of the velocity is the direction of the electromagnetic wave.

The wave is already moving towards the negative y axis (-j) and the magnetic field is already pointing towards the positive x axis (i)

From cross product of unit vectors

i × j = k

i × k = - j

With the second identity, we can see that the electric field will be pointing towards the positive of the x axis (k).

Option c is validated

4 0

3 years ago

Someone Help me please

natali 33 [55]

Answer:

a) Yes because spiderman isn’t part of the system (the train), so he exerts an external force on the system, causing it to slow. The sign is negative because the train is slowing negative.

b) The train was initially moving, so it had kinetic energy, the energy of movement. There isn’t the same amount anymore because spiderman did work onto the train. Work is defined by the change of kinetic energy of the system, so the train didn’t have the same amount of that type of energy at the end.

I hope this helps! :)

7 0

3 years ago

A 16.0 kg child on roller skates, initially at rest, rolls 2.0 m down an incline at an angle of 20.0° with the horizontal. If th

enyata [817]

The kinetic energy of the child at the bottom of the incline is 106.62 J.

The given parameters:

Mass of the child, m = 16 kg
Length of the incline, L = 2 m
Angle of inclination, θ = 20⁰

The vertical height of fall of the child from the top of the incline is calculated as;

$sin(20) = \frac{h}{2} \\\\h = 2 \times sin(20)\\\\h = 0.68 \ m$

The gravitational potential energy of the child at the top of the incline is calculated as;

$P.E = mgh\\\\P.E = 16 \times 9.8 \times 0.68\\\\P.E = 106.62 \ J$

Thus, based on the principle of conservation of mechanical energy, the kinetic energy of the child at the bottom of the incline is 106.62 J since no energy is lost to friction.

Learn more about conservation of mechanical energy here: brainly.com/question/332163

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2 years ago

Studen

Vesna [10]

Complete Question

A football coach walks 18 meters westward, then 12 meters eastward, then 28 meters westward, and finally 14 meters eastward.

From this motion what is the distance covered

What is the magnitude and direction of the displacement

Answer:

$D = 72 \ m$

Magnitude

$d = - 20 \ m$

Direction

West

Explanation:

From the question we are told that

The first distance covered westward is $d_w_1 = 18 \ m /tex] The first distance covered eastward is [tex]d_e1 = 12 \ m /tex] The second distance covered westward is [tex]d_w_2 = 28 \ m /tex] The second distance covered eastward is [tex]d_e2 = 14 \ m /tex] Generally the distance covered is mathematically represented as [tex]D = d_w1 + d_w2 + d_e1 + d_e2$

=> $D = 18 + 28 + 12 + 14$

=> $D = 72 \ m$

For the second question eastward is in the direction of the positive x-axis so it would be positive and westward is in the direction of the negative x-axis so it would be negative

The magnitude of the displacement is

$d = -d_w1 -d_w2 + d_e1 + d_e2$

=> $d = -18-28 + 12 + 14$

=> $d = - 20 \ m$

The direction is west

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3 years ago

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natulia [17]

I c
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. Fkfkkvkv

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3 years ago