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2 years ago

Jenny puts a book on her desk. she lifts the book up with her finger, using a force of 0.5N .The cover is 10cm wide .

Physics

1 answer:

zepelin [54]2 years ago

6 0

The turning moment on the cover of the book is 0.05 Nm.

Explanation:

Given:

Force applied (F) = 0.5 N

Distance covered (d) = 10 cm

Converting Distance covered from cm to meter we get (d)= 0.1 m

To find:

Turning Moment (M) on the cover of the book = ?

Formula to be used:

Turning Moment (M) = F × d

= 0.5 × 0.1

= 0.05 Nm

Thus the turning moment on the cover of the book is found to be 0.05 Nm

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A rock of mass m is thrown horizontally off a building from a height h. the speed of the rock as it leaves the thrower's hand at

Stells [14]

The correct answer is 3) $K_f = \frac{1}{2}mv_0^2 + mgh$ .

In fact, the total energy of the rock when it leaves the thrower's hand is the sum of the gravitational potential energy U and of the initial kinetic energy K:
 $E=U_i+K_i=mgh + \frac{1}{2}mv_0^2$
As the rock falls down, its height h from the ground decreases, eventually reaching zero just before hitting the ground. This means that U, the potential energy just before hitting the ground, is zero, and the total final energy is just kinetic energy:
 $E=K_f$ 
But for the law of conservation of energy, the total final energy must be equal to the tinitial energy, so E is always the same. Therefore, the final kinetic energy must be
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2 years ago

Plants use sunlight as energy to convert carbon dioxide and water into glucose and oxygen. Which best describes the reaction? Th

Alina [70]

Answer:

the correct statement is the first

The law of conservation of mass indicates the same amount of carbon will be found in the reactants as in the products.

Explanation:

The law of conservation of energy establishes that the masses are not destroyed, they can only be transformed.

Therefore the mass of carbon in the reactants (CO2 and H2O) must be in the products (glucose and oxygen)

so the correct statement is the first

The law of conservation of mass indicates the same amount of carbon will be found in the reactants as in the products.

6 0

2 years ago

Read 2 more answers

Two circular rods, one steel and the other copper, are joined end to end. Each rod is 0.750 m long and 1.50 cm in diameter. The

Eddi Din [679]

Answer:

(a) Steel rod: $1.1 * 10^{-4}$

Copper rod: $1.88 * 10^{-4}$

(b) Steel rod: $8.3 * 10^{-5} m$

Copper rod: $1.41 * 10^{-4} m$

Explanation:

Length of each rod = 0.75 m

Diameter of each rod = 1.50 cm = 0.015 m

Tensile force exerted = 4000 N

(a) Strain is given as the ratio of change in length to the original length of a body. Mathematically, it is given as

Strain = $\frac{1}{Y} * \frac{F}{A}$

where Y = Young modulus

F = Fore applied

A = Cross sectional area

For the steel rod:

Y = 200 000 000 000 $N/m^{2}$

F = 4000N

A = $\pi r^{2}$ (r = d/2 = 0.015/2 = 0.0075 m)

=> A = $\pi * (0.0075)^{2}$

=> A = 0.000177 $m^{2}$

∴ $Strain = \frac{4000}{200000000000 * 0.000177} \\\\Strain = \frac{4000}{35400000}\\ \\Strain = 0.000113 = 1.13 * 10^{-4}$

For the copper rod:

Y = 120 000 000 000 N/m²

F = 4000N

A = $\pi r^{2}$ (r = d/2 = 0.015/2 = 0.0075 m)

=> A = $\pi * (0.0075)^{2}$

=> A = 0.000177 $m^{2}$

$Strain = \frac{4000}{120 000 000 000 * 0.000177} \\\\Strain = \frac{4000}{21240000}\\ \\Strain = = 1.88 * 10^{-4}$

(b) We can find the elongation by multiplying the Strain by the original length of the rods:

Elongation = Strain * Length

For the steel rod:

Elongation = $1.1 * 10^{-4} * 0.75 = 8.3 * 10^{-5} m$

For the copper rod:

Elongation = $1.88 * 10^{-4} * 0.75 = 1.41 * 10^{-4} m$

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2 years ago

a 75 kg man is standing at rest on ice while holding a 4kg ball. if the man throws the ball at a velocity of 3.50 m/s forward, w

AysviL [449]

Answer:

His resulting velocity will be 0.187 m/s backwards.

Explanation:

Given:

Mass of the man is, $M=75\ kg$

Mass of the ball is, $m=4\ kg$

Initial velocity of the man is, $u_m=0\ m/s(rest)$

Initial velocity of the ball is, $u_b=0\ m/s(rest)$

Final velocity of the ball is, $v_b=3.50\ m/s$

Final velocity of the man is, $v_m=?\ m/s$

In order to solve this problem, we apply law of conservation of momentum.

It states that sum of initial momentum is equal to the sum of final momentum.

Momentum is the product of mass and velocity.

Initial momentum = Initial momentum of man and ball

Initial momentum = $Mu_m+mu_b=75\times 0+4\times 0 =0\ Nm$

Final momentum = Final momentum of man and ball

Final momentum = $Mv_m+mv_b=75\times v_m+4\times 3.50 =75v_m+14$

Now, initial momentum = final momentum

$0=75v_m+14\\\\75v_m=-14\\\\v_m=\frac{-14}{75}\\\\v_m=-0.187\ m/s$

The negative sign implies backward motion of the man.

Therefore, his resulting velocity is 0.187 m/s backwards.

3 0

2 years ago

A soccer player runs up behind a 0.450-kg soccer ball traveling at 3.20 m/s and kicks it in the same direction as it is moving,

NISA [10]

To develop this problem it is necessary to use the concepts related to Impulse.

The impulse is defined as the change in velocity at the rate of mass, that is

$L = m\Delta V,$

Where,

m = Mass

$\Delta V =$ Change in Velocity

This change in velocity can be expressed as,

$L = m(v_2-v_1)$

$L = 0.45*(12.8 - 3.2)$

$L = 0.45*9.6$

$L= 4.32 Kg.m/s$

Therefore the magnitude of the impulse is 4.32 Kg.m/s

7 0

2 years ago