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3 years ago

Why do scientists believe that dark matter exists even though it cannot be seen?

Physics

1 answer:

poizon [28]3 years ago

3 0

Because although they cannot see it, they can see it's influence on objects that can be seen, and it's effects.

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g A 1.45-kg block is pushed against a vertical wall by means of a spring (k = 860 N/m). The coefficient of static friction betwe

olga_2 [115]

Answer:

The minimum compression is $x= 0.046m$

Explanation:

From the question we are told that

The mass of the block is $m_b = 1.45 kg$

The spring constant is $k = 860 N/m$

The coefficient of static friction is $\mu = 0.36$

For the the block not slip it mean the sum of forces acting on the horizontal axis is equal to the forces acting on the vertical axis

Now the force acting on the vertical axis is the force due to gravity which is mathematically given as

$F_y = m_b*g$

And the force acting on the horizontal axis is force due to the spring which is mathematically represented as

$F_x = k *x * \mu$

where x is the minimum compression to keep the block from slipping

Now equating this two formulas and making x the subject

$x = \frac{m_b * g}{k * \mu}$

substituting values we have

$x = \frac{1.45 * 9.8}{860 *0.36}$

$x= 0.046m$

3 0

3 years ago

A block is pulled along a horizontal surface at a constant speed by a force (14.1i 0 j 5.1k). The direction k is perpendicular t

Pepsi [2]

Answer:

$W =84.6\ Nm$

Explanation:

given,

F = 14.1 i + 0 j + 5.1 k

displacement = 6 m

Assuming block is moving in x- direction

we know,

dW = F dx

$\int dW = F\int dx$

$W = F\int_0^6 dx$

$W = F[x]_0^6$

$W = 14.1 \times 6$

$W =84.6\ Nm$

hence, work done by the force is equal to $W =84.6\ Nm$

7 0

3 years ago

A 0.15-m straight wire moves with a constant velocity of 7.0 m/s perpendicularly

lana66690 [7]

Answer: force is 0.42 N

Explanation: F = l·v·B

8 0

2 years ago

A square loop of side length a =2.9 cm is placed a distance b = 1.2 cm from a long wire carrying a current that varies with time

daser333 [38]

Answer:

Explanation:

Magnetic field due to a long wire

B = ( μ₀ / 4π ) x 2 I / r ( I is current through the wire )

= (μ₀ Q t ) / ( 2 π r ) [ I = Q t ]

b ) Magnetic field will change through the length of the square shaped loop . So we shall have to take the help of integration to calculate the flux through the loop.

Flux Φ = ∫ B dA

=∫ ( μ₀ / 4π ) x 2 I / r dA

10⁻⁷ x 2 I ∫ a dr/r

2 x 10⁻⁷ x Qt x a [ ln (2.9+1.2) / 1.2 ]

4.6 x 10⁻⁷ x 2.9 x 10⁻² t ln 4.1 / 1.2

16.4 x 10⁻⁹ t

Φ( t ) = 16.4 x 10⁻⁹ t

Induced emf = dΦ( t ) / dt = 16.4 x 10⁻⁹ v

current

16.4 x 10⁻⁹ / 2.5

= 6.56 x 10⁻⁹

5 0

4 years ago

A simple pendulum is hollow from within and its time period is T. how is the time period of pendulum affected when:

goblinko [34]

The period of a pendulum is independent of the mass of the bob so whether it's empty or filled with something, the period remains the same.

$period = 2\pi \sqrt{ \frac{length}{g} }$

3 0

3 years ago