What was the probable speed of a vehicle travelling on a dry tarred road before a collision occurred if the driver braked hard to avoid a collision, causing the brakes to lock and to leave skid marks of 25 metres?

To determine the probable speed of the vehicle before the collision, we can use the concept of skid marks and the relationship between skid marks and speed.

The skid marks left behind by a vehicle depend on various factors, including the initial speed of the vehicle, the condition of the road, and the grip of the tires. When a vehicle brakes hard on a dry tarred road, and the brakes lock, it results in skid marks.

One common method to estimate the speed of a vehicle based on skid marks is to use the following formula:

Speed (in km/h) = √(30 × Skid marks (in meters))

Using the given information, we can substitute the value of the skid marks (25 meters) into the formula to find the speed:

Speed (in km/h) = √(30 × 25)
Speed (in km/h) = √(750)
Speed (in km/h) ≈ 27.39 km/h

Therefore, the probable speed of the vehicle before the collision was approximately 27.39 km/h.