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3 years ago

Which has more potential energy: a book on the floor or the same book on a table? Explain your answer.

Physics

1 answer:

sergij07 [2.7K]3 years ago

8 0

Answer:

The same book on a table has more potential energy.

Explanation:

The potential energy of a body on Earth is defined as the energy possessed by the virtue of its heights.

The equation for gravitation potential energy is given by

P.E = mgh joules

From the above equation it is evident that when there is a change in the value of 'h', there is a change in the value of P.E

So, as per the above equation, the potential energy of book on floor

P.E = m x g x 0 ∵ h = 0 at floor

P.E = 0

The same book on the table has some magnitude in 'h' greater than zero

So, the same book on a table has more potential energy.

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Which of the following elements is an alkali metal?

Scrat [10]

It is b. sodium because it is in group 1

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3 years ago

A hot-air balloon of diameter 12 mm rises vertically at a constant speed of 14 m/s. A passenger accidentally drops his camera fr

fgiga [73]

Answer:

The balloon is 66.62 m high

Explanation:

Combined Motion

The problem has a combination of constant-speed motion and vertical launch. The hot-air balloon is rising at a constant speed of 14 m/s. When the camera is dropped, it initially has the same speed as the balloon (vo=14 m/s). The camera has an upward movement for some time until it runs out of speed. Then, it falls to the ground. The height of an object that was launched from an initial height yo and speed vo is

$\displaystyle y=y_o+v_o\ t-\frac{g\ t^2}{2}$

The values are

$\displaystyle y_o=15\ m$

$\displaystyle v_o=14\ m/s$

We must find the values of t such that the height of the camera is 0 (when it hits the ground)

$\displaystyle y=0$

$\displaystyle y_o+v_o\ t-\frac{g\ t^2}{2}=0$

Multiplying by 2

$\displaystyle 2y_o+2v_ot-gt^2=0$

Clearing the coefficient of $t^2$

$\displaystyle t^2-\frac{2\ V_o}{g}\ t-\frac{2\ y_o}{g}=0$

Plugging in the given values, we reach to a second-degree equation

$\displaystyle t^2-2.857t-3.061=0$

The equation has two roots, but we only keep the positive root

$\displaystyle \boxed {t=3.69\ s}$

Once we know the time of flight of the camera, we use it to know the height of the balloon. The balloon has a constant speed vr and it already was 15 m high, thus the new height is

$\displaystyle Y_r=15+V_r.t$

$\displaystyle Y_r=15+14\times3.69$

$\displaystyle \boxed{Y_r=66.62\ m}$

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3 years ago

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azamat

Answer:

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Explanation:

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3 years ago

Read 2 more answers

An electric water heater consumes 2.5 kW for 1.9 h per day.

Alecsey [184]

Answer:

The cost of running the electric water heater for one year is 55.2391 $

Explanation:

The simple rule of 3 helps to quickly solve proportionality problems when you have three known values and one unknown. If two quantities are directly proportional (that is, when multiplying or dividing one of them by a number, the other is multiplied or divided respectively by the same number) the rule of three can be applied as follows:

a ⇒ b

c ⇒ x

So: $x=\frac{c*b}{a}$

where a, b and c are the known values and x is the value you want to find out.

In this case, you can first apply the following rule of three: if 2.5 kW are consumed in 1.9 hours, in 1 hour how many kW are consumed?

$kWh=\frac{1 h*2.5 kW}{1.9 h}$

kWh=1.316

So an electric water heater consumes 1.316 kWh in one day. You apply another simple rule of three: if the heater in 1 day consumes 1.316 kWh, in 365 days (1 year) how many kWh are consumed?

$kWh=\frac{365 days*1.316 kWh}{1 day}$