Question

Which of these IS an example of balanced forces? A. a book on a shelf B. air rushing out of a balloon C. rolling over and falling off the bed D. a car speeding up at a constant rate

Answer 1

Forces are balanced when net force on the object is zero or the sum of all force on the object is zero.

For book kept on a shelf, the weight of the book in down direction is balanced by the normal force on the book by the shelf. hence the book kept on a shelf is an example of balanced force.

In case of air rushing out of balloon , the balloon experience a net force by the air coming out of it.

rolling over and falling off the bed , the object falls under gravity force.

a car speeding up accelerates. since it accelerates , it has net force on it.