If a body of 4 kg is moving with valocity 5m/s and after sometime its valocity becomes 8m/s , then find the change in kinetic energy of the body.
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Answers
given: mass =4kg
final velocity, v =8m/s
initial velocity,. u=5m/s
change in kinetic energy=1/2×mv^2-1/2×mu^2
=1/2×4×8^2-1/2×4×5^2
=2×64-2×25
=128-50
=78J
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Given:-
→ Initial velocity of the body = 5m/s
→ Final velocity of the body = 8m/s
→ Mass of the body = 4kg
To find:-
→ Change in kinetic energy of the body
Solution:-
We know that :-
K.E. = ½mv²
Thus, change in K.E. :-
= Final K.E. - Initial K.E.
= ½mv² - ½mu²
= ½m[v² - u²]
= m/2[v² - u²]
Where :-
• m is mass of the body.
• v is final velocity of the body.
• u is initial velocity of the body.
By substituting values, we get :-
= 4/2[(8)² - (5)²]
= 2[64 - 25]
= 2×39
= 78 J
Thus, change in kinetic energy of the body is 78 J .
Some Extra Information:-
• Energy of a body is defined as the
capacity to do work.
• Kinetic energy is the energy possessed
by a body because of it's motion.
• Kinetic energy of a body is always
positive. This is beacuse mass can
never be negative and square of a real
value is always positive.