Question

If momentum decreases by 20%, KE will decreases by

• A. 40%
• B. 18%
• C. 36%
• D. 8%

Answer 1

Answer: (C)

36%

Answer 2

∆KE = $\frac { \mathrm { mv } ^ { 2 } } { 2 } - \frac { \mathrm { m } } { 2 } ( 0.8 \mathrm { v } ) ^ { 2 } = 0.36 \frac { \mathrm { mv } ^ { 2 } } { 2 }$

∴ decrease is 36%