T5 - Forces Flashcards
Feature of scalar quantities?
only have magnitude
Feature of vector quantities?
have magnitude and direction
What does length of arrow show in forces?
magnitude
what does direction of arrow show?
direction of vector quantity
what is a force?
a push or pull that acts on an object due to the interaction with another object.
What is a contact force?
when the objects are physically touching
What is a non-contact force?
when the objects are physically separated.
equation for weight?
weight(N)= mass(kg)× gravitationalfieldstrength (N/kg)
What is weight?
the force acting on an object due to gravity
Correlation between mass and weight of an object?
directly proportional
What is weight measured with?
Newtonmeter
What is the centre of mass?
The weight of an object at a single point
What is a resultant force?
a single force that has the same effect as all the original forces acting together
Equation for work done?
Work done(J) = Force(N) x Distance(m)
What is elastic deformation?
when elastic material returns to original shape when force is removed
What must happen to change shape of an object?
more than 1 force applied
What is inelastic deformation?
when inelastic materials do not return to original shape when force is removed
equation for force in elasticity?
force(N)= spring constant(N/m) × extension or compression(M)
What is the moment of a force?
turning effect of a force
equation for moment?
moment(Nm) = force(N) × distance(m)
What distance should be used for measuring moments?
perpendicular distance
What is a fluid?
a gas or liquid
What does the pressure in fluids to any surface?
a force at right angles to any surface.
Equation for pressure?
pressure(Pa) = right angle force of surface(N) / area of that surface(M^2)
What happens to density of atmosphere when altitude increases?
density decreases
Equation for column of liquid?
pressure(Pa) = height of the column(m) × density of the liquid(Kg/m^3) × gravitational field strength(N/kg)
Why does pressure of liquid increases with depth?
greater weight of liquid acting downwards
Why does pressure increase with density?
greater weight of liquid acting downwards
Why does the bottom of an object experience more pressure than the top in a liquid?
bottom is at a greater depth
What must happen for an object to float?
upthrust equals weight of object
What must happen for an object to sink?
upthrust less than weight of object
equation for speed?
speed = distance / time
What is the normal walking speed?
1.5 m/s
what is the running speed?
3 m/s
what is the cycling speed?
6 m/s
Factors that affect walking, running and cycling speed? x4
-age
-terrain
-fitness
-distance
What is speed of sound in air?
330 m/s
What happens to velocity when an object is moving around a circle in a constant speed?
velocity changes
equations for acceleration? x2
acceleration(m/s^2) = change in velocity(m/s) / time taken(s)
final velocity^2 − initial velocity^2 = 2 × acceleration × distance
How to find distance traveled in a velocity time graph?
area under graph
what is the acceleration of a free falling object under gravity near earths surface?
9.8 m/s^2
what eventually happens to an object falling through a fluid?
-resltant force goes to 0
-reaches terminal velocity
What is newtons first law of motion for a stationary object?
If the resultant force acting on an stationary object is 0, then the object remains stationary
What is newtons first law of motion for a moving object?
If the resultant force acting on a moving object is 0, then the object will continue moving in the same direction at the same speed
What is newtons second law of motion?
The acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object.
Equation for resultant force?
resultant force(N) = mass(kg) × acceleration(m/s^2)
How fast does a car travel on main road?
13 m/s
How fast does a car travel on motor way?
30 m/s
what is the acceleration required for a car on main road to go onto motor way?
2 m/s^2
what is the force required for a car on main road to go onto motor way?
2000N
What is inertia?
The tendency of objects to stay still or keep same motion
What is inertial mass?
a measure of how difficult it is to change the velocity of an object
What is newtons third law of motion?
Whenever two objects interact, the forces they exert on each other are equal and opposite.
What is the stopping distance of a vehicle?
sum of thinking distance and braking distance
Typical value range for reaction time?
0.2s-0.9s
Factors that affect thinking distance? x4
-tiredness
-drugs
-alcohol
-distractions
Factors that affect braking distance? x3
-wet and icy conditions
-worn tires
-worn brakes
what does large deceleration in vehicle lead to? x2
-brakes overheating
-loss of control
Equation for momentum?
momentum(kg m/s) = mass(kg) × velocity(m/s)
What is conservation of momentum?
In a closed system, the total momentum before an event is equal to total momentum after the event.
safety features for momentum? x5
-seat belt
-air bag
-bike helmet
-crash mat
-cushioned surface in playground
