A ball ? is always in neutral equilibrium. Explain.

Suggest two methods of improving the efficiency of a machine.

When I look at the tyres of a moving vehicle in a movie the look as if they are moving in the opposite direction. How can we explain this phenomenon/effect?

What is the effect on levels of liguid on a u-tube manometer when placed in a vacuum?

How would you measure the density of an irregular solid such as a glass stopper?

helicopter of mass 3000kg rises vertically at a constant speed of 25m/s if the acceleration due to gravity is10m/s2 ,determine the resultant force working on the helicopter