2. With regard to the pH scale, a solution with a pH

An object of mass 25kg is falling from the height h=10 m. calculate

r-ruslan [8.4K]

Answer:

a=2500J,b=1000K,c=1000J,d=14.142m/s

Explanation:

V²=U²+2gh

V²=0 + 2×10×10=200m/s

a).kinetic energy=(1/2)mv²=(1/2)25×200=2500

potential energy=mgh

p.e=25×10×10=2500J

pe+ke=2500+2500=5KJ

b).mgh=25×10×4=1000J

c). V²=U²+2gh

V²=0+2×10×4

V²=80

kinetic energy=(1/2)mv²

=(1/2)25×80

=1KJ

d). From my first paragraph V²=200

V=√200

V=14.142m/s

6 0

3 years ago

True or false?

Ksju [112]

1. False

Explanation: it's exactly the opposite. In fact, Lenz's law states that the induced current and the induced emf in a conductor are generated in such a direction that opposes to the change in magnetic flux through the coil. This is summarized by the negative sign in the Faraday's Newmann Lenz law:

$\epsilon= -\frac{d\Phi }{dt}$

where $\epsilon$ is the emf induced and $\frac{d\Phi}{dt}$ is the rate of change of magnetic flux through the coil.

Lenz's law is a consequence of the law of conservation of energy. In fact, we have:

- If the magnetic flux through a coil is increasing, then the induced current has a direction such that the magnetic field generated by the coil is opposite to the direction of the external magnetic field, in order to decrease the total flux

- If the magnetic flux through a coil is decreasing, then the induced current has a direction such that the magnetic field generated by the coil is in the same direction as the external field, in order to increase the total flux

2. False

Explanation: the magnetic flux through a surface is given by

$\Phi = BA cos \theta$

where

B is the magnitude of the magnetic field

A is the surface area

$\theta$ is the angle between the direction of B and the normal vector to the surface

As we see, the magnetic flux depends not only on B and A, but also on the orientation of the coil with respect to the magnetic field.

3. False

Explanation:

- Sound waves are mechanical waves: mechanical waves are waves consisting of oscillations of the particles in a medium. Due to their nature, therefore, mechanical waves can propagate only in the presence of a medium

- Electromagnetic waves are NOT mechanical waves: they consist of oscillations of electric and magnetic fields, in a direction perpendicular to the direction of propagation of the wave. Since em waves are not mechanical waves, they do NOT need a medium to propagate, since they can also travel through a vacuum; therefore the original statement is false.

5 0

2 years ago

Please answer D in the image with an explanation

puteri [66]

Answer:

The force is 274 N.

Explanation:

In figure 2:

(d) Let the tension in the string is T.

According to the Newton's second law,

Net force = mass x acceleration

Apply for 200N.

$T - 200 sin 35 =\frac{200}{9.8}\times a \\T - 114.7 = 20.4 a..... (1)\\220 - T = \frac{220}{9.8}\times a\\220 - T = 22.45 a..... (2)\\Adding both the equations\\334.7 = 42.85 aa =7.81 m/s^{2}$