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3 years ago

Calculate the hang time of an athlete who jumps a vertical distance of 0.75 meter

1 answer:

7 0

The time it takes going up will be equal the time returning: 
s = s0 + v0t + (1/2)at^2
Taking the top of the jump as 0 and positive direction downward,
h = 0 + 0 + (1/2)gt^2
t = √(2h/g)
Since the hang time will be twice the time to rise or fall, therefore:

T = 2t
T = 2√(2*0.75/9.80665)
T ≈ 0.78 seconds

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A coil formed by wrapping 65 turns of wire in the shape of a square is positioned in a magnetic field so that the normal to the

Fiesta28 [93]

Answer:

377 m

Explanation:

number of turns, N = 65

θ = 36°

B1 = 200 micro Tesla

B2 = 600 micro tesla

t = 0.4 s

induced emf, e = 80 mV

Let a be the side of the square coil.

$e=\frac{d\phi }{dt}=NA\frac{dB}{dt}\times Sinθ$

$0.080=\frac{65\times a^{2}\times Sin36\times\left ( 600 - 200 \right )\times 10^{-6}}{0.4}$

$0.080=0.038a^{2}$

a = 1.45 m

Total length of the wire, L = N x 4a = 65 x 4 x 1.45 = 377 m

Thus, the length of the wire is 377 m.

7 0

4 years ago

A 4 kg object moving to the left collides with and sticks to a 3 kg object moving to the right. Which of the following is true o

madam [21]

Answer:

D. The motion cannot be determined without knowing the speeds of the objects before the collision.

Explanation:

This question is tricky! We know the object moving to the left has a greater mass than the one moving to the right. We'd assume they would move to the left because the leftwards object has a greater mass, right?

Not. So. Fast.

We can solve for the objects' final velocity using the formula for momentum, m₁v₁ + m₂v₂ = (m₁ + m₂)v .

Now here's where the trap is sprung: we don't think about the equation. This shows that the final velocity of the objects and the direction depends on both the mass of the objects and their initial velocity.

Basically, what if the 3 kg object is moving at 1 m/s and the 4 kg object is moving at –0.5 m/s? The objects would move to the right after the collision!

Do we know the velocity of these objects? No, right?

That means we can't determine the direction of their motion unless we know their initial, pre-collision velocity. This question is tricky because we look at the 4 kg vs. 3 kg and automatically assume the 4 kg object would dictate the direction of motion. That's not true. It depends on velocity as well.

I hope this helps you! Have a great day!

4 0

3 years ago

A biconvex lens is formed by using a piece of plastic(n=1.70).

creativ13 [48]

Answer:

$f =17.15\ cm$

Explanation:

given,

refractive index of lens, n = 1.70

Radius of curvature of front surface. R₁ = 20 cm

Radius of curvature of the back surface, R₂ = 30 cm

focal length= ?

$\dfrac{1}{f}=(n-1)(\dfrac{1}{R_1}-\dfrac{1}{R_2})$

R₁ = +20 cm

R₂ = -30 cm

n = 1.70

$\dfrac{1}{f}=(1.70-1)(\dfrac{1}{20}-\dfrac{1}{-30})$

$\dfrac{1}{f}=0.70 \times 0.0833$

$f = \dfrac{1}{0.7 \times 0.0833}$

$f =17.15\ cm$

the focal length of the lens is equal to 17.15 cm

3 0

3 years ago

What respiratory structure controls breathing?

shutvik [7]

Lungs is what helps u breath

3 0

3 years ago

Read 2 more answers

A 12 oz can of soda is left in a car on a hot day. In the morning the soda temperature was 60oF with a gauge pressure of 40 psi.

Neko [114]

In this case, volume of the can remains constant. The relationship between pressure and temperature at constant volume is given by:

P/T = Constant

Then
$\frac{ P_{1} }{ T_{1} } = \frac{ P_{2} }{ T_{2} }$

Where
P1 = 40 psi
P2 = ?
T1 = 60°F ≈ 289 K
T2 = 90°F ≈ 305 K (note, 363 K is not right)

Substituting;
$P_{2} = \frac{ P_{1} T_{2} }{ T_{1} } = \frac{40*305}{289} =42.21 psi$

3 0

3 years ago