כוחות הם דחיפות ומשיכה השולטים בכל דבר ביקום. הם יכולים לגרום לדברים לזוז, להאיץ, להאט, לשנות כיוון, או אפילו לשנות את הצורה של דברים. הפעילויות הבאות יעזרו לתלמידים לתפוס כוח ותנועה כדי שיוכלו להבין טוב יותר את העולם הסובב אותם.
A Soyuz re-entry capsule just after the parachute has been released
שקופית: 4
A Soyuz re-entry capsule at rest on the ground
שקופית: 5
Thrust
Weight
Drag
The Soyuz orbital module is in orbit. Even though it's speed may be constant it's velocity is changing as it changing direction. Forces are unbalanced. The only force acting on the module is its weight.
שקופית: 6
Weight
The Soyuz orbital module is in orbit. Even though it's speed may be constant it's velocity is changing as it changing direction. Forces are unbalanced. The only force acting on the module is its weight.
שקופית: 7
Drag
Weight
The capsule is decelerating so the forces aren't balanced. The drag from the parachute must be larger than the weight of the parachute and the capsule.
שקופית: 8
Weight
Reaction force
The forces are balanced, as the capsule is not moving. The reaction force acting on the capsule from the ground is equal and opposite to the weight of the capsule.