Skip to content

ConquerYour A Levels

Home Subjects Competitive

Ctrl K

Search notes, subjects and papers.

Appearance

Create an account Sign in

Home Subjects Competitive

Friends Settings Profile

Appearance

Paper 4

Physics9702

Physics · 9702Paper 4

1.6Centripetal Force
1.7How Circular Motion Changes
1.8The Real Inward Force
1.9Resolving Forces in Circular Motion
1.10A Ball Inside a Smooth Cone
1.11Conical Pendulum
1.12Banked Roads & Aircraft
1.13Circular Motion at a Latitude

On this page

Resolving Forces in Circular Motion

Vertical and inward directions

Many circular-motion objects stay at the same height. Their vertical acceleration is zero.
The vertical force parts add to zero. The inward force parts add to $mv^2/r$ .
If a force F is at angle $\theta$ from the vertical, its vertical part is $F\cos\theta$ . Its inward part is $F\sin\theta$ .

Split an angled real force into a vertical part and an inward part. Use one equation for each direction.

Draw only the real forces.
Choose a vertical axis and an inward horizontal axis.
Write one equation for the vertical direction.
Write one equation for the inward direction.
Solve the two equations.

Worked example

A small component check

A 10 N force acts at 30° from the vertical. Find its vertical and horizontal components.

Find the vertical part.
$10\cos30^\circ=8.7\text{ N}$
Find the horizontal part.
$10\sin30^\circ=5.0\text{ N}$

Answer

\text{vertical part}=8.7\text{ N}

\text{horizontal part}=5.0\text{ N}

PreviousThe Real Inward Force NextA Ball Inside a Smooth Cone