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victus00 [196]
4 years ago
9

Suppose you wanted to start a fire using sunlight and a mirror. Which of the following statements is most accurate? A) It would

be best to use a plane mirror. B) It would be best to use a concave mirror, with the object to be ignited positioned halfway between the mirror and its center of curvature. C) It would be best to use a concave mirror, with the object to be ignited positioned at the center of curvature of the mirror. D) It would be best to use a convex mirror. E) One cannot start a fire using a mirror, since mirrors form only virtual images.
Physics
1 answer:
Maru [420]4 years ago
6 0
<h2>Answer: B) It would be best to use a concave mirror, with the object to be ignited positioned halfway between the mirror and its center of curvature. </h2>

Explanation:

To start a fire it is more optimal to use a concave mirror than a plane mirror. This is because the concave mirror allows concentrating sunlight at a point (the focal point) on an object that acts as fuel and ignite the fire there.

For this it is necessary the object to be  positioned between the center of curvature of the mirror and the mirror (its focus). Thus the rays of the Sun, when converging on the focus, will heat the object and make it burn.

Hence, the correct option is B.

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Using the Bohr model, what is the ratio of the energy of the nth orbit of a triply ionized beryllium atom (Be3+, Z = 4) to the e
emmainna [20.7K]

Answer:

16

Explanation:

solution:

by taking the ratio of the energy E_n,be of the nth orbit of a beryllium atom

Z_be=4 to the energy E_n,h of the nth orbit of a hydrogen (Z_h=1) atom  gives

E_n,B/E_n,H=-(2.18*10^-18)*Z^2_BE/-(2.18*10^-18)*Zh^2/n^2

                    =Z^2_BE+/Z^2_H

                    =(4)^2/(1)^2

                    = 16

8 0
4 years ago
To pull a box up a rough slope,the force required will be least when it is applied :
kaheart [24]

Answer:

The correct option is;

d) Parallel to the plane

Explanation:

The forces acting on the box of mass, m are;

Weight of the box acting an angle, θ, equal to the inclination of the plane to the perpendicular of the plane

Weight of the box acting along the plane = m×g×sin(θ)

The force of friction along the plane = μ×m×g×cos(θ)

The total force acting downward along the plane F_{down}, = m×g×sin(θ) + μ×m×g×cos(θ)

The Force needed to pull the box up along the plane F = The total force acting downward along the plane

F = m×g×sin(θ) + μ×m×g×cos(θ) = m×g×(sin(θ) + μ×cos(θ))

When the force, Fₐ is applied vertically, the force acting along the plane = Fₐ×cos(θ)

When the force is applied perpendicular, the force acting along the plane = Fₐ×sin(θ)

When the force is applied horizontally, the force acting along the plane = Fₐ×cos(θ)

When the force is applied parallel to the plane, the force acting along the plane = Fₐ

Therefore, since Fₐ > Fₐ×cos(θ) and Fₐ > Fₐ×sin(θ), for acute angles, we have that the least force is required when the force is acting parallel to the plane.

6 0
4 years ago
¡¡first convert revolutions per second to
katovenus [111]

Answer:

a. 5.23 m/s² b. 44.23 N

Explanation:

a. What is the centripetal acceleration of the  hammer?  

The centripetal acceleration a = rω² where r = radius of circle and ω = angular speed.

Now r = length of chain = 1.4 m and ω = 0.595 rev/s = 0.595 × 2π/s = 3.74 rad/s.

So a = rω²

= 1.4 m × (3.74 rad/s)²

= 5.23 m/s²

b. What is the tension in the chain?

The tension in the chain, T = ma where m = mass of hammer = 8.45 kg and a = centripetal acceleration of hammer = 5.23 m/s². This tension is the centripetal force on the hammer.

So, T = 8.45 kg × 5.23 m/s²

= 44.23 N

6 0
3 years ago
What frequency is received by a stationary mouse just before being dispatched by a hawk flying at it at 24.7 m/s and emitting a
Montano1993 [528]

Answer:

   f' = 3665.51 Hz

Explanation:

given,

speed of the hawk = 24.7 m/s

frequency of screech emitted by the hawk = 3400 Hz

speed of sound = 331 m/s

By Doppler's effect

f' = (\dfrac{v}{v-v_s}})f

f' is the frequency received by the mouse

v is the speed of the sound

v_s is the speed of the hawk

now,

f' = \dfrac{341}{341-24.7}}\times 3400

   f' = 1.078 x 3400

   f' = 3665.51 Hz

The frequency received by the stationary mouse is equal to 3665.51 Hz

6 0
3 years ago
When a 2.6 kg rock is thrown horizontally
Furkat [3]
It’s could be 8 because the rock is 2.6kg so it’s slow down
5 0
3 years ago
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