Question

10. An object of mass 40 kg is raised to a height of 5 m above the
ground. What is its potential energy? If the object is allowed to
fall, find its kinetic energy when it is half-way down.​

Answer 1

Answer:

1960J = potential energy

980J = kinetic energy

Explanation:

PE = mgh

= 40*9.8*5

= 1960 J

half way down height = 2.5m

S= 2.5m initial speed(u)= 0

v^2 = U^2 + 2gS

v = root( 2*9.8*2.5)

=7 m/s

so....KE = 1/2* mv^2

= 980J

hope it helps

^_^

Answer 2

Hey!

• Mass of the object = 40 kg.

• Height = 5 m (above the ground)

• Potential Energy = ?

• Kinetic energy in it's half way down = ?

• Potential Energy when it is at 5 m,

=> m*g*h = 40*10*5 = 2000 J

• Potential Energy at half way down i.e. 2.5 m

=> m*g*h = 40*10*2.5 = 1000 J

According to law if conservation of mass,

• Total potential energy = p.e at half way down + k.e at half way down.

• 2000 J = 1000 J + Kinetic Energy

• Kinetic Energy = 1000 J

IF, g = 9.8 m/s²

Then, P.E = m*g*h = 40*9.8*5 = 1960 J

At half way, P.E = m*g*h = 40*9.8*2.5 = 980 J

At half way, K.E = 1960 J - 980 J = 980 J.

Hope it helps!