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3 years ago

Electricity costs 10p per unit. How much will it cost Sam to use a 85W laptop and a 60W lamp for an hour?

1 answer:

6 0

The standard unit is KW/hr, = 1,000W/hr.
(85 + 60) = 145W.
You need to find its fraction of 1,000W., so (145/1000) = 0.145 KWH.
(0.145 x 10p) = 1.45p. per hr.

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Which statement explains how it is possible to carry books to school without changing the kinetic or potential energy of the boo

Mamont248 [21]

Answer:

a. by moving the book without acceleration and keeping the height of the book constant

Explanation:

FOR CONSTANT KINETIC ENERGY:

The kinetic energy of a body depends upon its speed according to its formula:

ΔK.E = (1/2)mΔv²

So, for Δv = 0 m/s

ΔK.E = 0 J

So, for keeping kinetic energy constant, the books must be moved at constant speed without acceleration.

FOR CONSTANT POTENTIAL ENERGY:

The potential energy of a body depends upon its height according to its formula:

ΔP.E = mgΔh

So, for Δh = 0 m/s

ΔP.E = 0 J

So, for keeping potential energy constant, the books must be moved at constant height.

So, the correct option is:

<u>a. by moving the book without acceleration and keeping the height of the book constant</u>

8 0

3 years ago

A 1000kg ar accelerates from rest to 25.0m/s in 4.20

bezimeni [28]

Answer:

74.4 kilowatts or 99.8 horsepower

Explanation:

The explanation is in the attachment.

7 0

3 years ago

Gravitational energy can be negative?

AlladinOne [14]

answer:

yes

explanation:

At a separation of the surface of Earth (r=6400km) gravity wants pull the test mass closer and closer. ... So the work done by gravity is NEGATIVE. The gravitational potential energy is negative because us trying to do the opposite of what gravity wants needs positive energy.

6 0

3 years ago

A 10-turn conducting loop with a radius of 3.0 cm spins at 60 revolutions per second in a magnetic field of 0.50T. The maximum e

bogdanovich [222]

Answer:

Maximum emf = 5.32 V

Explanation:

Given that,

Number of turns, N = 10

Radius of loop, r = 3 cm = 0.03 m

It made 60 revolutions per second

Magnetic field, B = 0.5 T

We need to find maximum emf generated in the loop. It is based on the concept of Faraday's law. The induced emf is given by :

$\epsilon=\dfrac{d(NBA\cos\theta)}{dt}\\\\\epsilon=NBA\dfrac{d(\cos\theta)}{dt}\\\\\epsilon=NBA\omega \sin\omega t\\\\\epsilon=NB\pi r^2\omega \sin\omega t$

For maximum emf, $\sin\omega t=1$

So,

$\epsilon=NB\pi r^2\omega \\\\\epsilon=NB\pi r^2\times 2\pi f\\\\\epsilon=10\times 0.5\times \pi (0.03)^2\times 2\pi \times 60\\\\\epsilon=5.32\ V$

So, the maximum emf generated in the loop is 5.32 V.

3 0

3 years ago

A flag bearer holds a 20 N flag at the end of a pole that has an angle of 20 degrees to the horizontal. What is the force from t

Nezavi [6.7K]

I think the answer is C) i am sorry if i am wrong plz let me know if i am wrong thank u.

4 0

3 years ago