mechanical · 28 minutes · Official OETT Aligned
Forces & Moving in a Circle
Pushes, pulls, and what happens when you let go
What to know
- pushes and pulls
- inertia: keeping the same motion
- moving in a circle
- tangent: the straight direction at release
These questions ask what makes an object change speed or direction.
The core rule
An unbalanced push or pull changes motion. When an object is released from a circle, it starts moving in the straight direction it was heading.
A force is a push or pull. Inertia means an object keeps moving the same way unless a force changes it. A stone on a string needs a pull toward the center to keep circling. If the string breaks, the stone starts along a tangent: a straight line that touches the circle at the release point. Gravity can then curve its path downward.
Worked examples
Example 1: easy
A stopped cart begins moving in the direction of a push.
- The cart is stopped. Find the direction of the push.
- With no equal force pushing back, the cart speeds up in that direction.
An unbalanced force changes how an object moves.
Example 2: medium
A stone on a string follows the tangent when the string breaks.
- Before the string breaks, it pulls the stone toward the center.
- When it breaks, that pull stops. The stone starts along the straight direction it was already heading.
This starting direction is the tangent, not a line straight out from the center.
Example 3: hard
At the top of a vertical loop, which way does the object move just after release?
- At the top of the loop, the line toward the center points down.
- The tangent is at a right angle to that line, so it points sideways. Use the rotation arrow to choose left or right.
The release direction follows the motion arrow at that exact point.
Common mistakes
The stone flies straight away from the center when the string breaks.
It first moves along the direction it was already heading, not straight out from the center.
Put it into practice
Use guided explanations, check your answers, and try a new variation.