Sound — Science STD 9 — Question

Explain why should we wear cotton clothes in summer.

Describe the term ‘inertia’ with respect to motion.

Bus X travels a distance of 360km in 5 hours whereas bus Y travels a distance of 476km in 7 hours. Which bus travels faster?

Name the articles which act as nucleus for water droplets to form around in the atmosphere.

Akhtar, Kiran and Rahul were riding in a motorcar that was moving with a high velocity on an expressway when an insect hit the windshield and got stuck on the windscreen. Akhtar and Kiran started pondering over the situation. Kiran suggested that the insect suffered a greater change in momentum as compared to the change in momentum of the motorcar (because the change in the velocity of the insect was much more than that of the motorcar). Akhtar said that since the motorcar was moving with a larger velocity, it exerted a larger force on the insect. And as a result the insect died. Rahul while putting an entirely new explanation said that both the motorcar and the insect experienced the same force and a change in their momentum. Comment on these suggestions.

Compare an electron and a proton in respect of mass and charge.

Explain why, a runner presses the ground with his feet before he starts his run.

Describe the term ‘inertia’ with respect to motion.