Govt. Exams
Entrance Exams
At the highest point, velocity is zero, but the gravitational force continues to act, producing an acceleration of g = 10 m/s² downward.
Normal force is a contact force arising from physical contact between the table and book. The action-reaction pair would be the weight of the book and the force the book exerts on the table.
When forces act in the same direction, the resultant is the sum of all forces: 10 + 20 + 30 = 60 N.
Newton's third law states action and reaction act on different bodies, not the same body. They are equal in magnitude, opposite in direction, and act simultaneously.
Using F = ma, we get a = F/m = 20/5 = 4 m/s².
From Newton's second law, F = ma. If F is constant and m doubles, then a = F/2m, so acceleration becomes half.
According to Newton's first law, when velocity is constant, acceleration is zero. Therefore, net force F = ma = m × 0 = 0 N.
