# How Is Newton's Third Law Applied in Calculating Forces on a Lawn Mower?

• F.B
In summary, the conversation discussed a complicated question involving a boy pushing a lawn mower with a given mass, force, and angle. The question asked for the magnitude of the normal force, frictional force, maximum velocity, and force needed to maintain constant velocity. The advice given was to divide the force into horizontal and vertical components and to consider the increase in normal force due to the push.
F.B
I hate all of Newton's laws questions. They are so complicated. Can anyone please help me with this question.

A boy pushes a lawn mower (m=17.9 kg) starts from rest across a horizontal lawn by applying a force of 32.9 N straight along the handle, which is inclined at an angle of 35.1 degrees above the horizontal. The magnitude of the mowers acceleration is 1.37 m/s^2, which lasts for 0.58 s, after which the mower moves at a constant velocity. Determine the magnitude of
a)the normal force on the mower
b)the frictional force on the mower
c)the maximum velocity of the answer
d)the force applied by the boy needed to maintain the constant velocity

Divide the force into horizontal and vertical components. Do remember to take into account the increase in normal force (the push is party directed vertically).

Applying Newton's third law, we know that for every action, there is an equal and opposite reaction. In this scenario, the boy is applying a force of 32.9 N on the lawn mower, but the lawn mower is also applying an equal and opposite force of 32.9 N on the boy. This reaction force is what allows the lawn mower to move forward.

a) The normal force on the mower is the force exerted by the ground on the mower in the opposite direction of the mower's weight. Since the mower is on a horizontal surface and is not accelerating vertically, the normal force will be equal and opposite to the weight of the mower, which is given by mg, where m is the mass of the mower and g is the acceleration due to gravity (9.8 m/s^2). Therefore, the normal force on the mower is 17.9 kg x 9.8 m/s^2 = 175.22 N.

b) The frictional force on the mower is the force that opposes the motion of the mower and is caused by the interaction between the mower and the ground. This force will be equal and opposite to the force applied by the boy on the mower, which is 32.9 N. Therefore, the frictional force on the mower is also 32.9 N.

c) The maximum velocity of the mower can be calculated using the equation v = u + at, where v is the final velocity, u is the initial velocity (which is 0 in this case), a is the acceleration, and t is the time. Therefore, v = 0 + (1.37 m/s^2 x 0.58 s) = 0.7966 m/s.

d) Since the mower is now moving at a constant velocity, the net force on the mower is 0. This means that the force applied by the boy on the mower must also be 0. In other words, the force required to maintain the constant velocity is 0 N.

## What is Newton's third law?

Newton's third law states that for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object will exert an equal force in the opposite direction on the first object.

## How is Newton's third law applied in real life?

Newton's third law can be seen in many everyday situations, such as when a person walks. The person's foot exerts a force on the ground, and the ground exerts an equal and opposite force back on the foot, propelling the person forward.

## What is an example of Newton's third law in physics?

One example of Newton's third law in physics is a rocket launching into space. The rocket exerts a force downward, pushing against the ground, and the ground exerts an equal and opposite force upward, propelling the rocket into the air.

## Why is Newton's third law important in understanding motion?

Newton's third law is important in understanding motion because it explains how forces interact and influence the movement of objects. Without this law, it would be difficult to predict the motion of objects and understand the forces acting on them.

## Can Newton's third law be violated?

No, Newton's third law is a fundamental law of physics and cannot be violated. For every action, there must be an equal and opposite reaction. If these forces are not balanced, the object will experience a net force and will accelerate.

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