Why is it difficult to walk on solid ice?

Why is it difficult to walk on a sand?

Why is it difficult to catch a cricket ball than a tennis ball even when both are moving with the same velocity?

Why is it difficult to shoot a fish swimming in water? (AS_(1))

Why is it more difficult to revolve a stone tied to a longer string than a stone tied to a shorter string ?

Why is it difficult for a fire fighter to hold a hose that ejects large amount of water at high speed?

(i) Can a body in translatory motion have angular momentum? Explain (ii) Why is it more difficult to revolve a stone by tying it to a longer string than by tying it to a shorter string?

Why is it difficult for DNA to pass through cell membrane ? How the bacterial cells can be made competent to take up DNA ?