# normal force Definition and Topics - 39 Discussions

In mechanics, the normal force

F

n

{\displaystyle F_{n}\ }
is the component of a contact force that is perpendicular to the surface that an object contacts, as in Figure 1. In this instance normal is used in the geometric sense and means perpendicular, as opposed to the common language use of normal meaning "ordinary" or "expected". A person standing still on a platform is acted upon by gravity, which would pull them down towards the Earth's core unless there were a countervailing force from the resistance of the platform's molecules, a force which is named the "normal force".
The normal force is one type of ground reaction force. If the person stands on a slope and does not sink into the ground or slide downhill, the total ground reaction force can be divided into two components: a normal force perpendicular to the ground and a frictional force parallel to the ground. In another common situation, if an object hits a surface with some speed, and the surface can withstand the impact, the normal force provides for a rapid deceleration, which will depend on the flexibility of the surface and the object.

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1. ### Is Gravity the only force doing work on a roller coaster cart?

Why I think gravity *is* the only force doing work on the rider: 1) The only forces acting on the rider are gravity and the normal force. Broken down into their component vectors, we have: -> The component of the force of gravity moving parallel to the rider's direction of motion -> The normal...
2. ### B Quick Question About Normal Force

Guys I was just wondering if normal force is a contact force. Obviously it is considered a contact force but it also has something to do with the repelling of atoms. In my mind, normal force is a fundamental truth, but technically, are two objects touching or is there a minuscule space between...
3. ### Free body diagram problem

Hello everyone. I find the following problem confusing. A board sandwiched between two boards in the figure below weighs 95.5N. If friction exists between the middle and the compressing boards, draw the free body diagram of the middle board. Below I attached the diagram found in the solution...
4. ### Question about Normal Force and Torque

Homework Statement A block of uniform density experiences a force F to the right, applied 5/3 m from the bottom of the block. The block is 2 m high and 1 m wide. Take the pivot point to be the point at the bottom right of the block. Find the value of the force that is just able to tip the box...
5. ### Automotive What is the compression force of a ring seated inside a cylinder

Hello. I am finding out how many normal force between ring and cylinder. I try to find around for many hours but get noting. there are 8.2 mm inner diameters than put in 8.6 mm cylinder. The hardness of sealing element is 55 ShA. Contact area is 48.63 mm^2. I have data and drawing in attachment...
6. ### System of equilibrium, why won't the normal force apply?

Homework Statement Homework Equations The Attempt at a Solution I've resolved all the relevant forces (tension, weight, normal force), but upon looking at the mark scheme, there is no normal force to be resolved. Forgive me if I'm missing out on something obvious, but shouldn't there be a...
7. ### A frictionless incline with a block sliding down it...

A frictionless incline (the triangle below) is bolted to the floor so that it can not move. A block of mass m slides down the slope, which makes an angle with the horizontal. a)Draw a free-body diagram for the block, labeling all forces uniquely. b)Describe all the forces listed above in the...
8. ### Help with finding Normal Force of inclined plane

So this is the problem: A 250-kg crate is on a rough ramp, inclined at 30° above the horizontal. The coefficient of kinetic friction between the crate and ramp is 0.22. A horizontal force of 5000 N is applied to the crate, pushing it up the ramp. What is the acceleration of the crate? Relevant...
9. B

### Forces on a plane exerted by a ball

Could someone please provide a diagram of all the forces acting on the plane, and explain why the answer is E? This is from the 2014 F=MA exam. Thanks, blueblast
10. ### B Can the normal force be in vertical direction?

HI, Can the normal force be in vertical direction ?
11. ### Magnitude of Frictional Force in Simple Harmonic Motion

Homework Statement I do not fully grasp the concept behind all of these sub questions (i)-(iv). Homework Equations v=wAcos(wt) (SMH)? Friction Force = Coefficient of Friction * Normal Force The Attempt at a Solution (i) Varying as simple harmonic motion sees varying acceleration as it...
12. ### How to find Torque without Coefficient of Friction?

Hello! I am an AP Physics student and had a quick question for validity. I was prompted with this question in class today: Example 7: An 8-meter ladder of weight 355 N leans at an angle of 50° to the floor against a smooth vertical wall. Assume the center of weight (gravity) for the ladder is at...
13. ### Normal Force between two concentric cylinders

Homework Statement a cylinder sits inside of another fixed cylinder without friction and an internal force acts on the cylinder as shown in the diagram. Draw the normal force vector and write down the force and moment equations. I drew in my normal vector to counteract the A force vector and...
14. ### B Does Normal force always HAVE to be perpendicular to plane ?

Say i Have 1. A perfectly spherical and perfectly rigid Ball 2. A perfectly flat and perfectly rigid wall Say i throw the ball at my FLAT wall also giving the ball a linear velocity The only contact with the wall and the ball is a point... a POINT !! So, I can as well forget about the rest of...
15. ### How does one find the normal force when not at constant velocity or at rest?

How does one find the normal force when the object is not at constant movement or at rest.
16. ### Centripetal Force, Friction, Loop de Loop, and Normal Forces

Two questions I had: 1. How is the force of friction of the tires pointed inwards to cause centripetal acceleration? If the tire is rotated when trying to turn, the car is still traveling with a velocity perpendicular to the circle and force of friction would still be counteracting the...
17. ### Four things -- Normal force, friction, Pressure, breakage

I understand that every force has an equal and opposite reaction, and the reason things can move is because the forces acts on different things. Also, F=MA is why the heavier object is accelerated less. The equal and opposite reaction to gravity pulling down towards the Earth's core on a book...
18. ### Came up with a problem that I can't solve

Imagine a hoop with mass M and radius R that will only roll without slipping on the floor. Place a point object with mass m on top of the hoop and then the system starts from at rest. Question: where does m leave M? If one fixes the hoop or let the hoop slide, solutions can be found using high...
19. ### Question about finding static friction coefficient

Homework Statement Two boxes each weighing 900 N are stacked on a horizontal floor. Box A is on the bottom, box B is on the top. The coefficient of static friction between box a and the floor is 0.3. A worker applies a force of 600 N to box b parallel to the floor, and the stack moves together...
20. ### B Elevator action-reaction pair/normal forces

In the above case, the normal force exerted by the elevator on the box would be = 10kg * g + 10kg*5m/s^2, assuming g = 10m/s^2, the elevator would exert a normal force of 150N on the box. But wouldn't the box exert an equal and opposite force on the elevator resulting in no motion? I know this...
21. ### Quantifying Inertial Resistance

Hi! I am having a little trouble with a question asked by a colleague. There’s a ball B with a certain mass M, at rest. A small ball A of mass m is moving with speed v toward M. If m=M, and the collision is perfectly elastic and the two objects perfectly rigid, than we know that A would come...
22. ### Work and Kinetic Energy of a Sled

Homework Statement A man pulls a 15-kg sled containing a 5.0-kg dog along a straight path on a horizontal surface. He exerts a force of 55 N on the sled at an angle of 20.° above the horizontal, as shown in the figure above. The coefficient of friction between the sled and the surface is 0.22...
23. ### Confusion about type and quantity of force being exerted

Homework Statement A 500-N person stands 2.5 m from a wall against which a horizontal beam is attached. The beam is 6 m long and weighs 200 N (see diagram below). A cable attached to the free end of the beam makes an angle of 45 degrees to the horizontal and is attached to the wall. a) draw a...
24. ### At what angle does the normal force go to zero?

Homework Statement An ice cube is placed on top of an overturned spherical bowl of radius r, as indicated in the figure. If the ice cube slides downward from rest at the top of the bowl, at what angle θdoes it separate from the bowl? In other words, at what angle does the normal force between...
25. ### Resolving forces in equilibrium on inclined plane

Homework Statement Solve for the forces P and N acting on an object in equilibrium on an inclined plane. Weight=10N, angle is 30 degrees http://blob:https%3A//www.physicsforums.com/d431a152-5681-411b-ba57-809320539165 Homework Equations Trigonometry, i.e. sin, cos, tan rules. The 'Z' rule...
26. ### Acceleration of a crate

Homework Statement At the instant shown, the driver of the truck has just pressed the accelerator pedal down and the truck has suddenly acquired a tangential acceleration of 2.2m/s^2. Coefficient of static friction between crate and tray = 0.4 Coefficient of kinetic friction between crate and...
27. ### Finding normal force

Please help with below. is it correct? A 41 kg crate rests on a horizontal floor and a 67kg person is standing on the crate. a. determine the magnitude of the normal force the floor exerts on the crate b. determine the magnitude of the normal force that the crate exerts on the person...
28. ### Discrepancy with Normal Force Problems

As I try to set up equations regarding Newtonian forces, I am looking for patterns in example problems I read. It's really frustrating then when I see different approaches that I can't see a connection to. There are two problems that I've attached that seem to solve - what seems to me about...
29. ### Normal Forces Between Two People on Top of each other

Homework Statement During an extreme stunt, a 45 kg cheerleader stands on the shoulders of a 55 kg cheerleader, while riding in a transparent elevator with an upward acceleration of 2 m/s2. Find the normal force between the cheerleaders and between the elevator and the bottom cheerleader...
30. ### Internal Force Diagram for Rigid Body and Distributed Load

I'm working on a homework problem for Statics and I'm stuck. Could someone please help? Problem: Draw the internal force (N,V,M) diagrams and include all significant figures Here is all of my work: Resulting F from W1: W(x) = W1 ∴ F2=∫02b W1dx eq (1) ⇒ F2 = W1⋅2b x1 = (F1)-1 ∫02b W1dx...