Question

Akari is using a gas lawn mower to cut the grass outside her home. Her young son Sergey is very curious and has left two small pebbles in the lawn, one in front of the living room window and one in front of the family car. When Akari passes over each pebble, the lawn mower propels the pebble into the living room window and then the side window of the car, respectively. Assuming the pebbles hit each glass surface with the same energy, and that the glass panels are the same thickness, which is the most probable of the following possible outcomes of these events?

(a) The living room window will break into many small pieces, while the car window will break into a few large pieces.

(b) The living room window will not break, while the car window will break.

(c) The living room window will break, while the car window will plastically deform.

(d) The living room window will break into a few large pieces, while the car window will break into many small pieces.

Answer 1

Option C sounds most probable for the following reasons:

1. The car window generally carries an additional coating of lamination (in addition to the glass layers) which makes it less sussceptible to breaking upon mild impacts or impacts by objects carrying relatively smaller quantum of momenta. On the other hand, the window glass in all likelihood would break and shatter into a few large pieces.

2. If its the front windshield of the car, it may not break at all, as the angle of approach of the pebble maynot be 90 degrees with the plane of the glass window.