Question

A girl, moving at 8.8 m/s on in-line skates, is overtaking a boy moving at 4.3 m/s as they both skate on a straight path. The boy tosses a ball backward toward the girl, giving it speed 11.4 m/s relative to him. What is the speed of the ball relative to the girl, who catches it?

Answer 1

Answer:16.5 m/s

Explanation:

Given

Velocity of boy$(v_b)=4.3 m/s$

velocity of girl$(v_g)=8.8 m/s$

velocity of ball relative to boy$(v_{Bb})=11.4 m/s$ backward

Now We have to find velocity of ball relative to girl

Representing it in vector form

$v_b=4.3\hat{i}$

$v_g=8.8\hat{i}$

$v_{Bb}=-11.4\hat{i}$

and

$v_{Bb}=v_B-v_b$

$v_B=v_{Bb}+v_b$

$v_B=-11.4\hat{i}+4.3\hat{i}=-7.1\hat{i}$

therefore velocity of ball relative to girl

$v_{Bg}=v_B-v_g=-7.1\hat{i}-8.8\hat{i}=-16.5\hat{i}$