PHYSICS HIGH SCHOOL

The total amount of electrical energy used by a315-watt television during 30.0 minutes of
operation is
(1) 5.67 × 10^5 J (3) 1.05 × 10^1 J
(2) 9.45 × 10^3 J (4) 1.75 × 10^1 J

Answers

Answer 1

Answer:

The amount of electrical energy used by the television is given by:

$E=Pt$

where P is the power of the device and t is the time.

The power of the television is P=315 W, while the total time is

$t=30.0 min \cdot 60 =1800 s$

If we substitute these numbers into the formula, we find the energy:

$E=Pt=(315 W)(1800 s)=5.67 \cdot 10^5 J$

so, the correct answer is

(1) 5.67 × 10^5 J

Answer 2

Answer: $W=Pt$
W - energy, P - power, t - time

$P=315 \ W \nt= 30 \ min= 30 * 60 \ s = 1800 \ s \n \nW=315 * 1800=567000=5.67 * 10^5 \ [J]$

The answer is (1).

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Karen shouts across a canyon and hears an echo 7.5 s later. how wide is the canyon? the speed of sound is 343 m/s. answer in units of m.

Answers

After Karen shouts, the sound wave of her voice travels across the canyon, it hits the walls, and then it comes back to Karen in a total time of t=7.5 s. If we call L the distance between Karen and the other side of the canyon (so, L is the width of the canyon), it means that the sound wave covers a distance of S=2L in this time.
Since the wave moves by uniform motion, we can use the usual relationship between space, time and velocity:
$v= (S)/(t)= (2L)/(t)$
where v=343 m/s is the speed of sound. Using this number, we can find L from the previous equation:
$L= (vt)/(2)= ((343 m/s)(7.5 s))/(2)=1286 m$
So, the canyon is 1286 meters wide.

Prudence means acting with ______.a.
Self restraint
b.
Fairness
c.
Caution
d.
Honesty

Answers

By definition we have to:

It is the capacity that the human being has to think at the moment of acting before certain activities, about the possible risks that these can have, and modify their behavior so as not to receive or produce unnecessary damages.

In other words we can say that prudence means acting with caution in certain activities.

Answer:

Prudence means acting with caution.

c.Caution

it means cautious :)

The term used to describe the quantity of matter that a body possesses is

Answers

The body mass index.

The term used to describe the quantity of matter that a body possesses is mass.

BY what factor does the kinetic energy of a moving body change when its speed is reduced to half? please help i have an exam and i need an answer

Answers

Answer:

Kinetic Energy = 1/2 mass*velocity^2

K=1/2mv^2

Therefore if you reduce the speed of an object by 1/2, K reduced to 1/4 its value.

Question 9How many neutrons are in an atom of Mg-25?
O 11
O 12
O
13
O 31

Answers

They differ only because a 24Mg atom has 12 neutrons in its nucleus, a 25Mg atom has 13 neutrons, and a 26Mg has 14 neutrons. Figure 2.3.

Answer:

number of neutrons = 13.

Explanation:

Each element is uniquely and completely identified by its Atomic Number. This is the number of protons in the nucleus, which is equal to the number of electrons in the neutral atom.The Atomic Number of Magnesium is 12.An atom’s Mass Number is the number of protons plus the number of neutrons in its nucleus.For Mg-25 the Mass Number is 25.So 25 = (number of protons) + (number of neutrons)= 12 + (number of neutrons)

A 1.7-kg block of wood rests on a rough surface. A 0.011-kg bullet strikes the block with a speed of 670 m/s and embeds itself. The bullet-block system slides forward 2.4 m before coming to rest.