Consider a man pushing a wall. No motion is involved. But both man and the wall experience force.Is it true?

Question

Acceleration is defined as instantaneous rate of change of velocity.Since no motion is involved how could we define the above.

Answer 1

There is more to the system than just the man and the wall. Let's say the wall and man are hovering in space and they push against each other. They would separate resulting in motion of both man and wall.

But on earth, when a man pushes against the wall and visa versa, they are both anchored to the ground. As the man pushes the wall, the wall would move but the earth is pushing on the wall the opposite direction. Likewise, as the wall pushes the man, the earth pushes him in the opposite direction through his feet. This can be illustrated by supposing the man were on ice and had no traction. He would surely glide away from the wall.

So how can there be force with no acceleration? Let's take the man's perspective. He is pushing on the wall resulting in a force the opposite direction, but he is also experiencing the earth pushing him towards the wall. Since both forces are equal and in opposite directions, the man's net force is zero. The same goes for the wall.

So, while your question is technically correct, you didn't take in account that there is more than one force involved, and those two cancel each other out.

Answer 2

Man Pushing Wall

Answer 3

True
2 Forces - Friction between the two surfaces and
- Normal Force - perpindicular to surface of contact.
The second being the most interesting one as its the force that prevents the person from penetrating the wall or the wall penetrating the person.
I dont know why I have seen words like accelleration and such, remember force is most well known as the influence that produces a change in a physical quantity. With no values at anypoint in the question, this man will continue to push this wall, and the wall will continue to be a wall.

Answer 4

Yes. The acceleration of a body is a function of the net of ALL forces acting on it. There are plenty of examples of forces without motion. A compressed spring, gravitational bodies in physical contact, a charged capacitor. The man applying 7 Newtons of force eastward on the wall is also applying 7 Newtons of force westward on the floor. His gravitational force is exactly matched by the contact force of the floor.

Answer 5

It is true that man and wall experience force. The man is applying a force against the wall and the wall is applying a "normal force" right back against him. With no motion involved that means that

1. the wall is pushing back on the man exactly as hard as he is pushing on it in the opposite direction

and of course the other way to look at it

2. the man is pushing back on the wall as hard as it's pushing on him (wall only pushes back against him if he pushes on it of course.. unless it's not attached to anything and is falling against him)

so for each object (wall and man) if you wanna solve for the TOTAL force on it (called net force) you will say okay we have force in some direction (say from man towards wall)... and another force in the opposite direction (from wall towards man).. what do you find? they cancel out exactly because they are in opposite directions and are the same strength!

so now when you are looking for your acceleration you can put in 0 as the value for F in F=ma
so 0 = ma
now you solve for a and you find that it's zero... because the net force on the object is nothing

It's just like a bone being pulled in exactly opposite directions by 2 dogs and each is just as strong as the other and there is no movement.. why? the forces were an equal match and they cancelled out. Or a book sitting on your shelf. It is being pulled down by the force of gravity yet it is standing completely still! why? because the shelf is hard and it's sitting on hard ground and it pushes back upwards with a "normal force" just as hard as gravity is trying to pull the book in towards the earth.

Answer 6

There is motion, his heart is accelerating, his circulatory system is speeding up and all the molecules in the wall are going faster from the pressure heat. You can define this as; Potential Energy, like a battery. When the wall breaks, you'll have your kinetic energy.

Answer 7

You are confused. Force can be calculated from acceleration, but force is always determined as the vector sum of all contributing forces. So lack of acceleration does not mean lack of force.

The same argument applies to gravity's force as well, which would have been a more obvious example.

Answer 8

yes it's true because the man pushing the wall is putting presher on it wich causes a force and with the man the wall and the wall not moving it puts a force between the man's hand and the wall.

Answer 9

There would be no acceleration because there is no net force; it is only when there is an unbalanced force when there is acceleration.

Answer 10

It is true. But mind you, although force is applied, there is no work done! Because, there is no displacement.