Question

an object of 1.9 kg of mass is thrown vertically upwards with an initial velocity of 5.50 m / s, assuming that the friction forces are minimal, then:

A. Determine the value of the kinetic energy at the moment when the object is thrown upwards.

B. If the moment the object leaves the hand is taken as the zero height, determine the value of the potential energy at that point.

C. Determine the highest point that the object reaches.

D. Determine the value of the potential energy at the highest point. E. Compare the values obtained in A and in D; They are different or the same. Why do you think this relationship between the values of potential and kinetic energies is presented?

Answer 1

here,

mass , m = 1.9 kg

initial velocity , u = 5.5 m/s

a)

the value of the kinetic energy at the moment when the object is thrown upwards , Ke = 0.5 * m * u^2

Ke = 0.5 * 1.9 * 5.5^2 J

Ke = 28.7 J

b)

If the moment the object leaves the hand is taken as the zero height,

the value of the potential energy at that point , Pe0 = m * g * h0

Pe0 = m * g * 0 = 0 J

c)

the highest point that the object reaches , h = u^2 /2g

h = 5.5^2/(2*9.81) m

h = 1.54 m

d)

the value of the potential energy at the highest point , Pe = m * g * h

Pe = 1.9 * 9.81 * 1.54 J = 28.7 J

c)

the values is A and D is same

when there is no external net force on the system

the total meachanical energy remains unchanged

total meachanical energy = KE + PE

so,

here

the kinetic energy lost = potential energy gained