A ball is dropped from height 20 m onto a horizontal floor. With g=10 m/s² and coefficient of restitution e=1/2, find total time (s) from release to the second bounce.
Physics · Mixed Chapter
JEE Main Practice

Question

A ball is dropped from height 20 m onto a horizontal floor. With g=10 m/s² and coefficient of restitution e=1/2, find total time (s) from release to the second bounce.

G1 Physics · Accepted Answer

Step 1: First fall takes t₁=√(2h/g)=√(40/10)=2 s. Step 2: Impact speed v₁=gt₁=20 m/s downward. After first bounce, upward speed u=e v₁=10 m/s. Step 3: The ball returns to floor after t₂=2u/g=2×10/10=2 s. Step 4: Time from release to second bounce =2+2=4 s.