Question

A boy slips and falls from a building at t = 0 s. After 6 s a girl jumps vertically down from the same
position of the building with a speed v. She catches that boy at t = 18 s. What is the value of v?​

Answer 1

ANSWER

The distance traveled by the first ball in 18s is h=  

2

1

​  

gt  

2

=  

2

1

​  

×10×(18)  

2

=1620m

Now to meet second ball has to same distance in(18−6)=12s

So for second ball,

h=vt+  

2

1

​  

gt  

2

 

1620=v×12+  

2

1

​  

×10×(12)  

2

 

v=  

12

1620−720

​  

=75m/s

Answer 2

The distance traveled by the first ball in 18s is h=  

2

1

​  

gt  

2

=  

2

1

​  

×10×(18)  

2

=1620m

Now to meet second ball has to same distance in(18−6)=12s

So for second ball,

h=vt+  

2

1

​  

gt  

2

 

1620=v×12+  

2

1

​  

×10×(12)  

2

 

v=  

12

1620−720

​  

=75m/s