Forces Flashcards
What is a scalar quantity?
A quantity that only has magnetude.
What is a vector quantity?
A quantity that has magnitude and direction.
What is typical driving speed (on a county road)?
80km/h
What is typical running speed?
3m/s
What is typical cycling speed?
6m/s
What is instantaneous speed?
The speed at a given point.
How do you find the speed on a distance time graph?
The gradient
What is the definition of constant speed?
When an object moves the same distance in equal intervals of time.
Why is circular motion at a constant speed accelerating?
- The object is changing direction
- So its volocity changes
- So it is accelerating
What is the force that causes circular motion?
A centripetal force, acting towards the cenre of the circle
How do you calculate distance on a velocity time graph?
The area under the graph.
How does normal reaction force work?
- Weight pushes down on particles
- This compresses the bonds between them
- The bonds push back against the weight
What is Newton’s third law?
If object A exerts a force on object B, then object B exerts an equal and opposite force on object A.
What is Newton’s first law?
An object at rest stays at rest and an object in motion stays in motion with the same speed and direction unless acted on by a resultant force.
What is inertia?
The resistance an object has to a change in its motion.
How does mass effect inertia?
The larger the mass - the larger the inertia
What is Newton’s second law?
Force = Mass x Acceleration
What is the relationship mass and acceleration?
They are inversely proportional
What is inertial mass?
A measure of how difficult it is to change the velocity of an object.
What is the center of mass of an object?
The point at which the weight of the object is considered to act.
What is gravity?
The force that causes anything with mass to be attracted to anything else with mass.
What is the value of acceleration due to gravity?
9.8m/s²
What is terminal velocity?
The maximum constant velocity of an object.
What is the relationship between force, and extension on a spring?
They are directly proportional
What is the spring constant?
A measure of how difficult it is to stretch/compress a spring.
What is the limit of elasticity?
The point where a larger force will result in the material loosing its elasticity.
What happens o the energy stored in a spring when it is inelastically deformed?
The elastic potential energy stored in it is no longer equal to the work done on it.
How do you calculate stopping distance?
Thinking distance + breaking distance
What is thinking distance?
The distance traveled while the driver thinks about breaking. Influenced by vehicle speed, and drivers reaction time.
What is breaking distance?
The distance traveled while the breaks are applied. Influeced by vehicle speed, mass, condition of vehicle, and condition of the road.
What is momentum?
The product of an objects mass and it’s velocity.
What is the principle of conservation of momentum?
In a closed system , the total momentum before an event s equal to the total momentum after the event.
What is an explosion
Where objects begin touching each other at rest, and then move apart.
What happens in perfectly inelastic collisions?
The masses stick together when they collide, creating a larger mass with a different volocity.
What happens in elastic collisions?
The masses bounce off each other and move in different directions.
How can the force of a collision be reduced?
By increasing the impact time.
What is a moment?
The turning effect produced by a force.
What is the unit of moments?
Newton meters (Nm)
What are the 2 ways that levers can be used?
- Force multipliers
- Distance multipliers
How do you find the ratio of moments for gears?
Ratio of moments = Ration of teeth = ratio of radii
Why does pressure increase with depth in fluids?
- More particle are above it
- More weight acting downwards
- Greater force acting over the same area
- So a greater pressure
Why do objects experience upthrust?
The bottom of the object has a greater pressure that the top, so it is pushed upwards.
When will an object float?
When upthrust is equal in size to the weight of the fluid that the object displaces.
Why does atmospheric pressure decrease with height?
- The air becomes less dense
- There are fewer molecules above a surface
- Fewer collisions with the surface
- So there is less pressure
