Forces 2 Flashcards
What is terminal velocity?
When a falling object stops accelerating due to the resultant force equalling zero and the resistive forces balancing the force of gravity.
What is Newton’s third law?
For every action there is, there is an equal and opposite reaction.
What is an example of Newton’s third law?
A rocket pushes fuel backwards, which, in turn, pushes the rock forwards.
What is momentum?
The product of mass and velocity.
What is the conservation of momentum?
In a closed system, the total momentum before an event is equal to there total momentum after the event.
How can momentum be applied to projectiles?
The recoil momentum of, for an example, a gun, is equal to the momentum of a bullet.
What does the stopping distance of a vehicle depend on?
The thinking distance (time taken for the driver to react).
The braking distance (time taken for the vehicle to stop).
What is the typical human reaction time?
0.4-0.9 seconds.
How can reaction time be affected?
Drugs, alcohol, fatigue, distractions.
How might the braking distance be affected?
Condition of the road.
Condition of the vehicle (worn brakes, under/over-inflated tyres).
The weather.
What happens with a greater breaking force.
The vehicle decelerates faster.
Describe the energy transfers in braking.
Work done by friction transfers the kinetic energy of the vehicle into heat energy.
What are implications of large decelerations?
Brakes may overheat.
Tyres may lose traction, which causes skidding.
Causes large forces to act on a person, which causes injury.
What are rules for working out braking distance?
Doubling the mass doubles the force required to break.
Doubling the speed quadruples the force required to break.
What is the acceleration of an object?
The measure of how quickly it speeds up, slows down, or changes direction.
