S2.6 Normal contact force
[A] About the force
The normal contact force FN is the repulsive force of interaction between two surfaces in contact, acting at right angles to the surfaces, and inhibiting closer contact.
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[B] Example problem
| Two bodies are free to move on a smooth horizontal surface under the action of a horizontal force of magnitude FA. |
Determine the acceleration and the normal contact force between them.
Solution
Reveal
Hide
Solution
- Let a be the acceleration to right (same for both bodies)
- Choose a system comprising both masses.
Apply 2nd law:
FA=(m1+m2)aimplying
- Choose a system comprising 2nd mass alone.
Apply 2nd law: FN=m2aso![\[ \xmlInlineElement[\xmlAttr{}{target}{slides}]{http://www.ph.ed.ac.uk/aardvark/NS/aardvark-latex}{aardvark:reveal}{a=\frac{F_N}{m_2}} \]](mastermathpng-1.png)
Eliminate a:
![\[ \frac{F_N}{m_2} =\frac{F_A}{m_1+m_2} \]](mastermathpng-2.png)
Hence

Results
acceleration:
Check It!
- Are the units OK?
- Does it make sense?
Learning Resources
| HRW Chapter 5.7,5.9 | |



