Since the two blocks are connected by the rope of the pulley, they will have the same acceleration and we can treat them as a single system. Start by drawing a free-body diagram including all the forces acting on each object.  Also, choose a direction to be considered the positive direction (+) and a direction to be the negative direction (-).

Each block has two forces acting on it: weight and tension. The weight of each block can be found using the equation:

Therefore, the weight of the 10 kg block is 100 N, and the weight of the 15 kg block is 150 N.

According to Newton's third law, for every force there is an equal and opposite force. The two tension forces, in this case, are an action/reaction pair; they are equal in magnitude but opposite in direction.

Now, using Newton's second law:

Since we are treating the system as a whole, or as if it is moving as a single object, we will add up all the forces acting on each object.

All forces which point in the positive (+) direction, as shown in the free body diagram above, will also be positive when put into the equation. All forces pointing in the negative (-) direction will also be negative in the equation.

What should we use for "" in the equation? Since we are treating the whole system as a single object, we must add all the masses together. In other words, 10 kg plus 15 kg, which is 25 kg total mass.

Notice now that the two tension forces will be canceled out, since they are action/reaction pairs and thus are equal but opposite in sign. So, solve for acceleration:

Dave weighs 589 N. This means his mass is

He accelerates at , which means he was pushed by a force of

By Newton's third law of motion, Dave must also have pushed of the ground with a force of 240 Newtons.

Consistent with Newton's third law, which states that every force has an equal and opposite reaction, the force on the rifle is equal to the force on the bulet. However, the rifle has a larger mass, so the magnitude of its acceleration is less than that of the bullet.

The cars will experience the same force, due to Newtown's third law. Because the larger car experiences the same force and has a larger mass, by Newton's first law, it will have a smaller acceleration. 

By Newton's third law, for every reaction there is an equal and opposite reaction. The floor must exert a 7N force upwards on the chair for the system to remain at rest. If it exerted less than that, the chair would be accelerating into the floor. This force, exerted by a surface, perpendicular to it, is called the normal force.

The relative mass of two interacting objects does not influence the magnitude of the force that the two objects exert on each other. Newton's third laws states the force must be equal in magnitude. If you're trying to reconcile how a football player is unable to "hit harder" than someone who does not lift weights, the answer lies in Newton's second law.

The football player weighs more and thus experiences a small acceleration. The smaller gentleman experiences a large acceleration due to his relatively small mass. This large acceleration is what we view when we see a large football player hit someone smaller. The football player hardly changes his motion while the smaller person will fly backwards. 

While all three laws come into play in a car crash only one is specifically responsible for keeping a person restrained in their seat. Just before the crash, the passenger is moving along at the same speed as the car. When the car collides into the other car and decelerates, the person's body continues to move forward. This is Newton's first law, or the law of inertia. But it is Newton's third law that keeps the person from being ejected from their seat. The force of the person's body moving forward was matched by that of the seatbelt. For every action there is an equal and opposite reaction. If the seat belt was unable to "match" the force of the person's body moving forward against it, it would have snapped and the person would have continued forward.

This is Newtons's third law. Every action has an equal an opposite reaction. The reason the train is able to move at all is due to the force the locomotive puts on the rails, which enables it to accelerate the cars.

By Newton's third law, every action has an equal and opposite reaction. So the force has an equal and opposite force on the other block. Mathematically, this just means to negate the force.

The correct answer is because of Newton's Third Law which states that for every action there is an equal and opposite reaction, so when Jake pushes Ross he also exerts the force he uses on himself. With this plus the force Ross exerts on Jake we arrive at our answer of