Friction is the force that tries to stop two materials that are touching from moving past each other.
Air resistance is friction between a moving object and the air. It reduces speed, which is bad for fast sports where a fraction of a second can make all the diffrence.
Friction between materials isn't always a bad thing, though it depends on the piece of equipment. If there were no friction between your shoes and the ground, you'd slip up when you tried to walk.
Designers try to minimise or maximise friction to get the best out of the equipment and sportswear.
If sports clothing is uncomfortable, it could be distracting and affect performance.
If the clothing is to heavy you need to put in extra effort to move around.
Any equpment is sterilised to kill off any unwanted microorganisms.
Disinfectants, antibacterial cleaners and bleach are all chemicals that kill microbes. they're used for cleaning work surfaces and floors.
Detergents, washing up liquid and washing powers disolve grease, oil and dirt. They deprive the microorganisms of the food they have to live.
Heat can be used to kill all the microbes on equipment, steam is often used to do this. in the home we used steam to sterilise things as babies bottles.
Kitchen bins are a giant bredding ground for microorganisms and they attract pests like rats and cockroaches.
First the Police will arrive at the crime scene and make sure that the crime scene is empty and safe.
They will stop any unauthorised people from entering the crime scene, the may also cover up any evidence that might blow away or washed away by rain. This prevents the evidence from being disturbed and stops any foreign material being introduced into the crime scene.
It also stops someone planting evidence or removing vital evidence.
They wear protective clothing to prevent contaminating the crime scene with anything thats on themselves or on their shoes, e.g- hair or mud.
This also protects the scienctists from potentially harmful substances at the crime scene, e.g - hair, blood or chemicals.