Question

The following tables list the masses, speeds, and heights of $5$ different objects. Which one has the greatest kinetic energy?

• A. $Mass=10kg,Speed=5m/s,Height=50m$
• B. $Mass=5kg,Speed=9m/s,Height=40m$
• C. $Mass=7kg,Speed=8m/s,Height=30m$
• D. $Mass=20kg,Speed=2m/s,Height=70m$
• E. $Mass=8kg,Speed=7m/s,Height=50m$

Answer 1

The correct option is C $Mass=7kg,Speed=8m/s,Height=30m$

Kinetic energy $K.E=\frac{1}{2}m{v}^2$

(A) : $K.E_A=0.5\times 10\times 5^2=125$ J

(B) : $K.E_B=0.5\times 5\times 9^2=202.5$ J

(C) : $K.E_C=0.5\times 7\times 8^2=224$ J

(D) : $K.E_D=0.5\times 20\times 2^2=40$ J

(E) : $K.E_E=0.5\times 8\times 7^2=196$ J

Hence option C has the greatest kinetic energy.