A ball of mass 2 kg and another of mass 4 kg are dropped together from a 60 ft tall building. After a fall of 30 ft each towards earth, their respective kinetic energies will be in the ratio of

Question

A ball of mass 2 kg and another of mass 4 kg are dropped together from a 60 ft tall building. After a fall of 30 ft each towards earth, their respective kinetic energies will be in the ratio of (A)  √2:1  (B)  1:4  (C)  1:2  (D)  1:√2

Tardigrade Admin · Accepted Answer

In a free fall, two balls of different mass will acquire the same velocity after falling through same height.
From key idea,

v_{1} = v_{2} = v

at a

30 f t

from falling point.
Here,

m_{1} = 2 k g, m_{2} = 4 k g

Thus,

\frac{K _{1}}{K _{2}} = \frac{\frac{1}{2} m _{1} v ^{2}}{\frac{1}{2} m _{2} v ^{2}}

= \frac{m _{1}}{m _{2}} = \frac{2}{4} = \frac{1}{2}

Q. A ball of mass $2 k g$ and another of mass $4 k g$ are dropped together from a $60$ ft tall building. After a fall of $30$ ft each towards earth, their respective kinetic energies will be in the ratio of

$2 : 1$

$1 : 4$

$1 : 2$

$1 : 2$

Q. A ball of mass 2kg and another of mass 4kg are dropped together from a 60 ft tall building. After a fall of 30 ft each towards earth, their respective kinetic energies will be in the ratio of

2​:1

1:4

1:2

1:2​

In a free fall, two balls of different mass will acquire the same velocity after falling through same height. From key idea, v1​=v2​=v at a 30ft from falling point. Here, m1​=2kg,m2​=4kg Thus, K2​K1​​=21​m2​v221​m1​v2​ =m2​m1​​=42​=21​

Q. A ball of mass $2 k g$ and another of mass $4 k g$ are dropped together from a $60$ ft tall building. After a fall of $30$ ft each towards earth, their respective kinetic energies will be in the ratio of

$2 : 1$

$1 : 4$

$1 : 2$

$1 : 2$