According to the third law of motion when we push on an object,the object pushes back on us with an equal and opposite force.If the object is a massive truck parked along the roadside, it will probably not move. A student justifies this by answering that the two opposite and equal forces cancel each other.Comment on this logic and explain why the truck does not move.
When the object is at rest or uniform motion, there is mass or weight of object which is always acts downward, and there is a static friction between object and floor and its equal to weight on object. When a car is at rest, to move the car, one has to apply a force more than the static friction. So, this applying force is greater than static friction hence the car is at verge of motion. But in case of truck, the truck has a large mass. The static friction between the truck and the road is also very high. Hence, student applying the force on truck and truck does not move, then it can be said that the applied force in one direction is cancelled out by the frictional force of equal amount acting in the opposite direction. Therefore, the student is right in justifying that the two opposite and equal forces cancel each other.
