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Sedaia [141]
3 years ago
6

Just need to confirm an answer

Physics
1 answer:
Citrus2011 [14]3 years ago
5 0

Answer:

B

Explanation:

Remark

If, when it reaches its maximum height where the PE is the greatest, that the maximum energy is when the ball is first kicked. That would mean its starting energy is 10 Joules.

Formula

KE = 1/2 m v^2

Givens

KE = 10 J

m = 0.2 kg

v = ?

Solution

10 = 1/2 * 0.2 * v^2

10 * 2 = 0.2 * v^2

20 = 0.2 * v^2

20/0.2 = v^2

100 = v^2

v = 10 m/s

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A student attaches a rope to a 20.0 kg box of books. He pulls with a force of 90.0 N at an angle of 30 degrees with the horizont
kolbaska11 [484]

Answer:

The magnitude of the acceleration of the box is 2.01 m/s².

Explanation:

Hi there!

Please, see the attached figure for a graphical description of the problem.

We have the following horizontal forces:

Fr = friction force.

Fx = Horizontal component of the applied force, F.

And we have the following vertical forces:

Fy = vertical component of the applied force.

N = normal force exerted on the box.

W = weight of the box.

According to Newton´s second law:

∑F = m · a

Then, in the horizontal direction:

Fx - Fr = m · a

Where "m" is the mass of the box and "a" its acceleration.

Fx can be obtained by trigonometry (see figure):

Fx = F · cos 30°

Fx = 90.0 N · cos 30°

Fr is calculated as follows:

Fr = μ · N

Where μ is the coefficient of friction and N the normal force.

So, we have to find the magnitude of the normal force.

Using Newton´s second law in the vertical direction:

∑F = N + Fy - W = m · a

Notice that the box has no vertical acceleration, then:

N + Fy - W = 0

Solving for N:

N = W - Fy

The weight is calculated as follows:

W = m · g

Where g is the acceleration due to gravity:

W = 20.0 kg · 9.8 m/s² = 196 N

And the vertical component of the applied force can be obtained by trigonometry:

Fy = F · sin 30°

Fy = 90.0 N · sin 30°

The normal force will be:

N = W - Fy = 196 N - 90.0 N · sin 30°

N = 151 N

Now, we can calculate the friction force:

Fr = μ · N

Fr = 0.250 · 151 N

Fr = 37.8 N

And now, we can obtain the acceleration of the box:

Fx - Fr = m · a

(Fx - Fr) / m = a

(90.0 N · cos 30° - 37.8 N ) / 20.0 kg = a

a = 2.01 m/s²

The magnitude of the acceleration of the box is 2.01 m/s².

8 0
3 years ago
A parallel-plate vacuum capacitor has 8.38 J of energy stored in it. The separation between the plates is 2.30 mm. If the separa
Elanso [62]

Answer:

Explanation:

plate separation = 2.3 x 10⁻³ m

capacity C₁ = ε A / d

= ε A / 2.3 x 10⁻³

C₂ = ε A / 1.15 x 10⁻³

\frac{C_2}{C_1} = \frac{2.3}{1.15}

a ) when charge remains constant

energy = \frac{q^2}{2C}

q is charge and C is capacity

energy stored initially E₁= \frac{q^2}{2C_1}

energy stored finally E₂ = \frac{q^2}{2C_2}

\frac{E_1}{E_2} = \frac{C_2}{C_1} = \frac{2.3}{1.15}

E_2 = \frac{1.15}{2.3 } \times E_1

= \frac{1.15}{2.3 } \times 8.38

= 4.19 J

b )

In this case potential diff remains constant

energy of capacitor = 1/2 C V²

energy is proportional to capacity as V is constant .

\frac{E_2}{E_1} = \frac{C_2}{C_1}

\frac{E_2}{8.38} = \frac{2.3}{1.15}

E_2 = 16.76 .

8 0
3 years ago
You kick a soccer ball straight up into the air with a speed of 21.2 m/s. How long does it take the soccer ball to reachbits hig
Dimas [21]
Gravity increased the downward speed (or decreases the upward speed) by 9.8 m/s every second.

21.2/9.8 = 2.2 seconds
7 0
3 years ago
Read 2 more answers
Question 8 of 25
Dima020 [189]

Answer:

B.

Explanation:

8 0
3 years ago
Two coconuts fall freely from rest at the same time, one from a tree twice as high as the other. If the coconut from the shorter
valentinak56 [21]

Wee can use here kinematics

as we know that

y = v*t + \frac{1}{2} at^2

for shorter tree we know that

y = 0 + \frac{1}{2}*9.8 * 2^2

y = 19.6 meter

now since we know that other tree is twice high

So height of other tree is y = 39.2 m

now again by above equation

y = v*t + \frac{1}{2} at^2

39.2 = 0 + \frac{1}{2}*9.8 * t^2

t = 2.83 s

so the time taken is 2.83 s

4 0
3 years ago
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