Susan and her friend found a piece of metal which they want to identify. Here is what they figure out so far:
Mass of this metal is 74 g
Volume of this metal is 40 cm3

The given  metal is beryllium.

Explanation:

Given data:

Mass of metal = 74 g

Volume of metal = 40 cm³

Which metal is this = ?

Solution:

First of all we will calculate the density.

it is mass divided by volume.

d = m/v

d = 74 g/40 cm³

d = 1.85 g/cm³

In literature it is given that the density of beryllium is 1.85 g/cm³. Thus given  metal is beryllium.

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j