2: Forces and Motion - YK Flashcards
(9 cards)
What is force and what is its unit?
Force is anything which causes acceleration
Force = mass * acceleration (F=ma)
Unit: Newtons (N)
What is a free-body diagram?
A free-body diagram shows all of the forces that act on a single object.
What are mass and weight?
Mass is a measure of how much matter is in an object, weight is the force of gravity acting on mass.
What do Newton’s laws state?
1st Law: A body will remain at rest or moving at constant speed unless acted on by an external force
2nd Law: The rate of change of momentum per unit time is directly proportional to the applied force, and takes place in the direction of the applied force
3rd Law: Every action has an equal and opposite reaction
What forces are involved in circular motion?
Centripetal force is needed to keep the object in circular motion (by applying a force towards the centre of rotation), if the force is removed the object would continue in a straight line, circular motion can have constant speed but changing velocity (direction changes - acceleration changes).
What is friction and drag?
Friction is the force opposing the sliding motion between two objects, reducing speed and converting kinetic energy to other forms (slowing, heating, wearing away, or statically charging objects). Lubricants are substances which act to lower friction. Drag is the force opposing motion in a fluid.
What is momentum and impulse?
Momentum = mass * velocity (p=mv)
In any interaction total momentum is constant (conservation of momentum)
Impulse = change in momentum
Force = change in momentum / time
How is momentum related to car safety measures?
Stopping a moving car requires a change in momentum. Airbags, seatbelts, and crumple zones all decrease the force by increasing the time taken, reducing the risk of injury to passengers.
What factors are involved in stopping distance?
Stopping distance = thinking distance + braking distance
Thinking distance = reaction time * vehicle speed
Thinking distance is affected by alertness (inhibited by alcohol, drugs, and fatigue) and reaction time
Braking distance depends on momentum, brake condition, tyre condition (grip), type of road surface, whether the road is lubricated (with water or oil)
