Answer: Option B. -> Nylons
The plastic material commonly used for making gear wheels is nylons.

Answer: Option A. -> Refraction
The apparent depth will look less that its real depth due to the refraction of light. Refraction is the bending of a wave when it enters a medium where it’s speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the normal to the boundary between the two media. The amount of bending depends on the indices of refraction of the two media and is described quantitatively by Snell’s Law.

Answer: Option C. -> Both A & B
Simple machine make work easier and work input > work output.

Answer: Option A. -> A pair of scissors
Any of the basic mechanical devices for applying a force are called simple machines.
There are 6 basic simple machines; the lever, the wheel and axle, the inclined plane, the wedge, the pulley, and the screw. Several of these simple machines are related to each other. But, each has a specific purpose in the world of doing work. A pair of scissors is not a simple machine.

Answer: Option A. -> Refraction
When light passes from one medium to another, this phenomenon of change in its direction is called refraction.

Answer: Option C. -> Radius vector
In uniform circular motion, the linear velocity is perpendicular to radius vector.

Answer: Option D. -> Yes, since they help to absorb the impact of a collision and keep the occupants safe
In automobiles, a bumper is the front-most or rearmost part, ostensibly designed to allow the car to sustain an impact without damage to the vehicle’s safety systems. They are not capable of reducing injury to vehicle occupants in high-speed impacts, but are increasingly being designed to mitigate injury to pedestrians struck by cars.

Answer: Option A. -> Four times
Brake force, also known as Brake Power, is a measure of braking power of a vehicle. Suppose a car whose mass is ‘x’ and is braked from a speed of y km/hr to come to halt at a uniform retardation in z min. If the speed of the car is doubled in the same distance, then the braking force required to stop the car is four times the original speed i.e. ‘4v’. Note that all the parameters remain to be same.

Answer: Option B. -> Helps the engine in keeping the speed uniform
A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia and thus resist changes in rotational speed, enabling the engine to run at a constant, uniform motion. In the Industrial Revolution, James Watt contributed to the development of the flywheel in the steam engine.

Answer: Option D. -> Alpha Particle
Since alpha particle has higher mass than electron, proton and deuteron, its momentum will be maximum.