# The rear view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rear view mirror the image of a truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be (i) 1 m/s (ii) 2 m/s (iii) 4 m/s (iv) 8 m/s

Navjyot Kalra
askIITians Faculty 654 Points
9 years ago

(iii) 4 m/s

The speed of the car is 2 m/s which means the car is approaching the truck with a speed of 2 m per second. The distance between the car and truck will decrease at a double rate. This is because the image of the truck will travel a distance twice the distance travelled by the car in equal time. Hence, the image of the truck will appear to approach the driver with the speed of 2 ×2 = 4 m/s.

askIITians Faculty 628 Points
2 years ago
Dear student,

The speed of the car is 2 m/s which means the car is approaching the truck with a speed of 2 m per second.
The distance between the car and truck will decrease at a double rate.
This is because the image of the truck will travel a distance twice the distance travelled by the car in equal time.
Hence, the image of the truck will appear to approach the driver with the speed of 2 ×2 = 4 m/s.

Thanks and regards,
Kushagra
Janarth
92 Points
2 years ago

(iii) 4 m/s

The speed of the car is 2 m/s which means the car is approaching the truck with a speed of 2 m per second. The distance between the car and truck will decrease at a double rate. This is because the image of the truck will travel a distance twice the distance travelled by the car in equal time. Hence, the image of the truck will appear to approach the driver with the speed of 2 ×2 = 4 m/s.