Natural Resources — Science STD 9 — Question

A boy tries to push a truck parked on the roadside.The truck does not move at all. Another boy pushes a bicycle moves through a certain distance. In which case was the work done more: on the truck or on the bicycle? Give a reason to support your answer.

How many moles of O₂ are there in 1.20 × 10²² oxygen molecules?

The kinetic energy of an object of mass, m moving with a velocity of 5ms^–1 is 25J. What will be its kinetic energy when its velocity is doubled? What will be its kinetic energy when its velocity is increased three times?

The power output of an engine is 3kW. How much work does the engine do in 20s?

What is the work done against gravity when a body is moved horizontally along a frictionless surface?

Why do we irrigate our crops?

What is the significance of the formula of a substance?

When is the work done said to be negative?

The velocity of a body of mass 10kg increases from 4m/s to 8m/s when a force acts on it for 2s.
What is the gain in momentum per second?