Forces and Motion Flashcards
Define scalar quantity and give 2 examples
It is a magnitude and it can be described fully with a single numerical value.
Ex: distance, speed, time, energy…
Define vector quantity and give 2 examples
Has both magnitude and direction.
Ex: Force, velocity, displacement, moment…
Which property of a distance-time graph can be used to calculate speed?
The gradient.
Equation linking distance, time and speed with units.
speed(m/s)=d(m)/t(s)
d/v x t
What is meant by acceleration? Give its unit.
Acceleration is the change in velocity per unit of time. (m/s²)
State an equation linking acceleration, change in velocity and time taken.
Acceleration=(change in velocity)/time
a=(v-u)/t
v-u/a x t
v:final velocity u:initial velocity
Which property of a velocity-time graph can be used to calculate acceleration?
Gradient
Which property of a velocity-time graph can be used to calculate distance travelled?
Area under the graph
State an equation linking final speed, initial speed, acceleration and distance travelled.
v²=u²+2as
Name 2 types of forces that always oppose motion
- Friction
2.Air resistance
Which type of force holds electrons around nucleus?
Electrostatic Force.
State the ways a force can affect the body that is being applied on.
-Shape of the object.
-Speed
-Direction
State an equation linking unbalanced force, mass and acceleration.
Force (N) =Mass (kg) x Acceleration (m/s²)
F= m x a
State an equation linking mass, weight and gravitational acceleration
Weight (N) = Mass (kg) x g(m/s²)
W=m x g
What is the relationship between stopping distance, breaking distance and thinking distance of a car whilst stopping?
Stopping dist=Thinking dist + Breaking dist
State 7 factors that affect the stopping distance of a car
-Reaction time
-Initial speed
-Road conditions
-Tire conditions
-Weather conditions
-Driver’s conditions
-Mass of the car.
2 factors that affect the air resistance acting on a falling object.
-Surface area
-Speed
Describe how a falling object reaches to terminal velocity.
-First, the object falls under the effect of its weight accelerating with gravity
-As it accelerates air resistance opposing the motion increases and since F=ma acceleration decreases.
-When air resistance becomes equal to weight, forces are balanced so resultant force=0 thereforce a=0 and object reaches terminal velocity.
State what is meant by obeying Hooke’s law
Extension is directly proportional with the force applied
Explain the difference between elastic and plastic behaviour.
Elastic behaviour: Object recovers its original shape when the forces causing the extension is removed.
Plastic behaviour: There is a permanent deformation to the shape of the object when forces are removed.
State an equation linking mass, velocity and momentum
P= m x v
Momentum (kgxm/s)=Mass (kg) x velocity (m/s)
Explain what is meant by conservation of momentum
Total momentum before a collision (or explosion) is equal to total momentum after the collision (or explosion)
State an equation linking force, change in momentum and time
Force= change in momentum/time taken
F= mv-mu/t
F=ΔP/t
Explain how safety features such as seatbelt, crumple zone and airbags reduce risk of injury in accident
All of these safety features increases the stopping time during a collation by applying a force for longer period of time. Since ΔP=FxT and ΔP is constant, as stopping time increases, force applied on the driver decreases therefore the risk of injury decreases.
Explain what Newton’s third law of physics states about forces
Newton’s third law states “for every action, there is an equal but opposite reaction.” This means all forces comes in pairs. Within these pars two forces have equal size but they act on different bodies in opposite direction.
What is the centre of gravity?
Point where all the weight of the object acts
For uniform objects, its in the middle point of the object
As centre of gravity gets lower, stability increases.
a) What is meant by moment?
b)When does it occur?
c)Is it scalar or vector?
a) Turning effect of the force
b) It occurs when a force applied away from the pivot (turning point), of the object perpendicularly
c) It is a vector quantity. It can be clockwise or anticlockwise
How do you calculate the moment of a force?
Moment= Force x Perpendicular distance from pivot
The direction is referred to as either clockwise or anticlockwise
State two conditions for an object to be considered in equilibrium
-Forces must be balanced (no resultant force)
-Clockwise moment = Anticlockwise moment
