Final answer:
The correct answer is (2) Same, as tires should have the same minimum tread depth to ensure even grip and control across all tires for safe operation of a vehicle.
Step-by-step explanation:
The question 'You need at least what tread in the front tires and what tread in other tires?' is concerning the minimum tread depth that should be present on vehicle tires for safe operation. For safety, tire tread depth should be the same on all tires to ensure even grip and control. The legal minimum tread depth varies by country, but a common standard is 2/32 inches or 1.6 millimeters. Tires with insufficient tread depth cannot effectively displace water on wet roads and may result in reduced traction on ice and snow. Therefore, it's essential to have adequate tread depth on all tires, not just the front tires.
When driving on different surfaces, the coefficient of friction (μ) between the tires and the surface changes. Dry concrete will have a higher μ, wet concrete will have a lower μ, and ice will have a much lower μ, assuming μ = 0.100. This reduced friction on ice necessitates special winter tires that can create more friction than summer tires.
Another example where more friction is desirable is when using sports equipment, such as running shoes with traction on a track or rubber grips on tennis rackets. These are designed to increase friction between the equipment and the contact surface to enhance performance and safety.