A car is backing up at a rate of 10km/hr. If the driver looks through his rear-view mirror, how fast does a tree, which is behind him, appear to approach him?

4 m/s

Nothing

To determine how fast the tree appears to approach the driver, we need to consider the relative motion between the car and the tree.

Since the car is backing up, its velocity can be considered negative (-10 km/hr). Let's assume the velocity of the tree is v km/hr.

The apparent approach speed of the tree can be calculated by taking the difference between the velocities of the car and the tree:

Apparent Approach Speed = Velocity of Car - Velocity of Tree

Given:
Velocity of Car = -10 km/hr

Therefore, the apparent approach speed of the tree can be expressed as:

Apparent Approach Speed = (-10) - v

Thus, the apparent approach speed of the tree relative to the driver, while the car is backing up at a rate of 10 km/hr, can be defined as (-10) - v km/hr.

To determine how fast the tree appears to approach the driver, we need to consider the relative motion between the car and the tree. Suppose the car is moving backward at 10 km/hr and the tree is stationary.

When the driver looks through his rear-view mirror, the image he sees is affected by this relative motion. The apparent motion of the tree is caused by the difference in velocity between the car and the tree.

Since the car is moving toward the tree (in the opposite direction), the apparent motion of the tree will be the sum of the car's speed and the tree's speed. In this case, since the tree is stationary, the apparent motion is the same as the car's speed.

Therefore, when the driver looks through his rear-view mirror, the tree will appear to approach him at a speed of 10 km/hr.