Question

A metal ball of mass 60 g falls on a concrete floor from a vertical height of 2.8m and rebounds to a height of 1.3 m. Find the change in K.E. in S.I. units.

Answer 1

Mass(m) = 60 g = 0.06 kg
Height(h) = 2.8 m
Acceleration due to gravity(g) = 9.81 m/s^2

v^2 - u^2 = 2gh

v^2 - 0 = 2(9.81)(2.8) = 54.936

v = 7.41 m/s.

Kinetic Energy(KE) = (1/2)mv^2

= (1/2)(0.06)(7.41)(7.41)

= 1.64 J.

After rebounds,

v^2 = 2(9.81)(1.3) = 25.506

v = 5.05 m/s.

KE = (1/2)(0.06)(25.506)

= 0.76 J.

Difference in KE = 1.64 - 0.76 = 0.88 J.

-WonderGirl

Answer 2

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