Answer:
Using lighter material in car construction, improving energy efficiency by enhancing engine design or replacing the engine with more efficient technologies.
Explanation:
Using lighter materials in the car construction, reducing the potential energy required to accelerate and to move the car, as well as energy losses due to rolling friction. There is evidence of such benefits by replacing steel and aluminium parts with components made of composite materials.
Improving the design of internal combustion engines to minimize energy losses and accordingly, improving energy efficiency. A more radical approach is replacing internal combustion engines with electric engines, which offer higher efficiencies. Such conclusions can be easily inferred from model based on Work-Energy Theorem and Principle of Energy Conservation:

Answer:

Explanation:
It is given that,
Mass of the grindstone, m = 3 kg
Radius of the grindstone, r = 8 cm = 0.08 m
Initial speed of the grindstone, 
Finally it shuts off, 
Time taken, t = 10 s
Let
is the angular acceleration of the grindstone. Using the formula of rotational kinematics as :



Let
is the number of revolutions of the grindstone after the power is shut off. Now using the third equation of rotational kinematics as :





or

So, the number of revolutions of the grindstone after the power is shut off is 50.