Swings are usually made out of materials that do not conduct heat easily, so that children will not burn themselves as they play

What is the difference between density and specific gravity

lys-0071 [83]

Density is defined as mass per unit volume. It has the SI unit kg m-3 or Kg/m-3 and is an absolute quantity. Specific gravity is the ratio of a material's density with that of water at 4 °C (where it is most dense and is taken to have the value 999.974 kg·m-3). It is therefore a relative quantity with no units.

4 0

3 years ago

The circumference of the earth is 40,000 km. The distance from the

Finger [1]

Answer:

The distance from the North Pole to the equator is $1*10^{7}$ m.

Explanation:

Circumference of Earth = 40,000 km ......................(1)

Distance from the North Pole to the Equator is = 1/4th of the Circumference of Earth ...................... (2)

Let Distance from the North Pole to the Equator be d ,

the equation formed will be ,

d = 1/4 * Circumference of Earth ........(3)......... ( from equation 1 )

put the value of Circumference of Earth in equation (3),

d = 1/4 * 40,000 km

d = 10,000 km

converting km to m ,

d = 10,000 * $10^{3}$ m

d = 1 * $10^{7}$ m

The distance from the North Pole to the equator is $1*10^{7}$ m.

7 0

3 years ago

A 1-kg block is lifted vertically 1 m at constant speed by a boy. The work done by the boy is about:

Igoryamba

Answer:

$9.8\; {\rm J}$ , assuming that the gravitational field strength is $g = 9.8\; {\rm N \cdot kg^{-1}}$ .

Explanation:

Notice that both the speed and the direction of motion of this block are constant. In other words, the velocity of this block is constant.

By Newton's Second Law, the net force on this block would be $0$ . External forces on this block should be balanced. Thus, the magnitude of the (downward) weight of this block should be equal to the magnitude of the (upward) force that the boy applies on this block.

Let $m$ denote the mass of this block. It is given that $m = 1\; {\rm kg}$ . The weight of this block would be:

$\begin{aligned}\text{weight} &= m\, g \\ &= 1\; {\rm kg} \times 9.8\; {\rm N \cdot kg^{-1}} \\ &= 9.8\; {\rm N}\end{aligned}$ .

Hence, the force that the boy applies on this block would be upward with a magnitude of $F = 9.8\; {\rm N}$ .

The mechanical work that a force did is equal to the product of:

the magnitude of the force, and
the displacement of the object in the direction of the force.

The displacement of this block (upward by $s = 1\; {\rm m}$ ) is in the same direction as the (upward) force that this boy had applied. Thus, the work that this boy had done would be the product of: