An object that looks white when exposed to sunlight reflects all colors of light. What

A cord is used to vertically lower an initially stationary block of mass M = 3.6 kg at a constant downward acceleration of g/7.

dalvyx [7]

Answer:

(a) $W_c=127.008 J$

(b) $W_g=148.176 J$

(c) K.E. = 21.168 J

(d) $v=3.4293m.s^{-1}$

Explanation:

Given:

mass of a block, M = 3.6 kg

initial velocity of the block, $u=0 m.s^{-1}$

constant downward acceleration, $a_d= \frac{g}{7}$

$\Rightarrow$ That a constant upward acceleration of $\frac{6g}{7}$ is applied in the presence of gravity.

∴ $a=- \frac{6g}{7}$

height through which the block falls, d = 4.2 m

(a)

Force by the cord on the block,

$F_c= M\times a$

$F_c=3.6\times (-6)\times\frac{9.8}{7}$

$F_c=-30.24 N$

∴Work by the cord on the block,

$W_c= F_c\times d$

$W_c= -30.24\times 4.2$

We take -ve sign because the direction of force and the displacement are opposite to each other.

$W_c=-127.008 J$

(b)

Force on the block due to gravity:

$F_g= M.g$

∵the gravity is naturally a constant and we cannot change it

$F_g=3.6\times 9.8$

$F_g=35.28 N$

∴Work by the gravity on the block,

$W_g=F_g\times d$

$W_g=35.28\times 4.2$

$W_g=148.176 J$

(c)

Kinetic energy of the block will be equal to the net work done i.e. sum of the two works.

mathematically:

$K.E.= W_g+W_c$

$K.E.=148.176-127.008$

K.E. = 21.168 J

(d)

From the equation of motion:

$v^2=u^2+2a_d\times d$

putting the respective values:

$v=\sqrt{0^2+2\times \frac{9.8}{7}\times 4.2 }$

$v=3.4293m.s^{-1}$ is the speed when the block has fallen 4.2 meters.

6 0

3 years ago

archer shoots his arrow towards a target at a distance of 90 m, and hits ‘bullseye’ . Calculate the acceleration and time taken

Cerrena [4.2K]

Answer:

Acceleration = 45m/s^2
Time = 2 s

Explanation:

6 0

4 years ago

Which is not a source of electrical energy in the United States

xenn [34]

Every practical source of energy that you can imagine, as well as a few impractical ones, are used somewhere in the USA.

From whale oil in Alaska, to nuclear energy, to coal, petroleum, natural gas, solar energy, wind energy, and biomass.

Oh ! Geothermal energy and tidal energy aren't too popular, but I'll bet if you looked, you'd find these used too, SOMEwhere in the 50 states.

7 0

3 years ago

A cell phone uses a 3. 0 V battery. The circuit board it uses needs a 0. 05 A current. What size resistor is needed to generate

Marta_Voda [28]

The value of resistance will be 60 ohms. Resistance is the opposition force offered to the flow of electric current. The ratio of the voltage to the electric current passing through the wire.

<h3>What is a resistor?</h3>

A resistor is a two-terminal passive electrical component that acts as a circuit element by implementing electrical resistance.

Resistors are used to limit current flow, alter signal levels, divide voltages, bias active devices, and complete transmission lines in electronic circuits.

The given data in the problem is;

V is the voltage = 3. 0 V

I is value of electric current= 0. 05 A

R is the resistance=?

According to ohm's law, the potential difference between the two ends of the conductor is equal to the product of electric current and the resistance generated.

So from the ohm law;

V= IR

$\rm R = \frac{V}{I} \\\\ \rm R = \frac{3}{0.05} \\\\ \rm R =60 \ ohm$

Hence the value of resistance will be 60 ohms.

To learn more about the resistor refer to the link;

brainly.com/question/1322424

3 0

2 years ago

An atom of sodium (Na) gives up an electron to chlorine (Cl) to form table salt. What type of bond is this?

Alexxx [7]

Your answer will be C!~

6 0

4 years ago