Question

At the local farm you buy a flat of strawberries and place them on the back seat of the car. On the way home, you begin to brake as you approach a stop sign. At first the strawberries stay put, but as you brake a bit harder, they begin to slide off the seat. Which of the following statements are correctly describing this situation?

A. When the car moves at constant speed, Newton's first law applies. When the car slows down, Newton's second law applies.

B. The frictional force between seat and strawberries is zero if the car moves at constant speed.

C. The static force between seat and strawberries slows down the strawberries during the car breaking.

D. Newton's 1st law is not true for a non-inertial frame of reference.

E. The static frictional force between seat and strawberries gives the strawberries an acceleration "a" equal to the car's acceleration only for low values of "a".

F. The breaking car is a non-inertial frame of reference

G. The frictional force between seat and strawberries appears only during the breaking and causes the slow down of the strawberries.

H. With respect to an observer at rest on the road, the flat of strawberries keeps moving in the same direction and is slowed down by the kinetic friction with the seat.

Answer 1

The first option would be correct. Because as the car moves in a particular direction, the strawberries will also be in the motion in that direction. When there is a constant speed, the Newton first law is applicable here as it states that the body would be in the motion unless an external force applies on it. Later on when the brakes applied, there is a negative acceleration and hence there would be reaction by the strawberry as their inertia was in motion first