p4 Flashcards
What is Newtons third law?
Newton’s third law is: When two objects interact, the forces they exert on each other are equal and opposite.
What is a force?
A force is a push on an object that is caused by it interacting with another object.
What is a gravitational force?
A gravitational force is the attractive forces between the Earth and the Sun.
What is electrostatic forces?
The attraction or repulsion of charges when their electric fields interact.
What is magnetic forces?
The attraction or repulsion between two magnets due to their magnetic fields
What is the definition of an interaction pair?
An interaction pair is whenever two objects both feel a force of some kind, either a push or a pull.
What is mass?
Mass is measured in kilograms and is just the amount of matter in an object.
What is weight?
Weight is a downwards force between an object and the Earth, it is a gravitational attraction.
Weight(N)=
Mass(kg) x gravitational field strength(N/kg)
What are scalar quantities?
Examples of scalar quantities are: speed, distance, time- they simply tell you the “size” of the thing you’re measuring nothing else.
What are vector quantities?
Examples of Vector quantities are velocity, displacement, acceleration- vector quantities tell you both the size of the thing and its direction.
What is the difference between speed and velocity?
The difference between speed and velocity is that speed only states how fast something is but velocity states both how fast something is and the direction it is going in.
What is displacement?
Displacement is a vector quantity, it measures the net distance and direction in a straight line from an objects starting point to an objects finishing point.
Is distance a scalar or vector quantity?
Distance is a scalar quantity because it doesn’t state the direction in which the object is moving.
What is the equation of average speed?
Average speed= distance/time
What is the average wind speed?
The average wind speed is 7m/s.
What is acceleration measured in?
Acceleration is measured in metres per second squared.
What is the equation for acceleration?
change in speed / time taken
What is the definition of acceleration?
Acceleration is the change in velocity of an object in a certain amount of time.
What do distance time graphs tell you?
Distance time graphs tell you how far something has travelled.
What do the flat sections on a distance time graph show?
The flat sections on a distance time graph shows that the object isn’t moving.
What do curved sections on a distance time graph show?
The curved sections on a distance time graph show that there is acceleration.
What does a levelling off curve on a distance time graph show?
A levelling off curve on a distance time graph shows that the object is slowing down.
What are velocity time graphs used to find?
Velocity time graphs can be used to find average acceleration.
What do flat sections on a velocity time graph show?
Flat sections on velocity time graphs show that the object is moving at a steady pace.
What do uphill (/) sections on a velocity time graph show?
Uphill sections on a velocity time graph show that the object is accelerating. But a straight uphill line means it is a constant acceleration whereas a curve means it is a changing acceleration.
How can you calculate the acceleration on a velocity time graph?
You can calculate the acceleration on a velocity time graph by finding the gradient of a tangent at that point.
What do free body diagram show?
Free body diagrams show all the forces acting on an object.
What is the resultant force?
The resultant force is the overall force on a point or object.
What if the resultant force on an object is 0?
If the resultant force on an object is 0 the object will not move.
What is Newton’s first law?
Newton’s first law says that a resultant force is needed to change the motion of an object.
What dos momentum equal?
Momentum= mass x velocity
What does Newton’s second law say?
Newton’s second law says that change in momentum is proportional to the size of the resultant force and the time over which the force acts on the object.
What does change in momentum equal?
Change in momentum= resultant force x time for which it acts.
What is the law of conservation of momentum?
In a collision when no other external forces act, momentum is conserved- i.e.- the total momentum after a collision is the same as it was before it.
What is the equation for force?
Force= mass x acceleration
What does resultant force equal?
Resultant force= change of momentum / time
What does inertia mean?
Inertia is the tendency for an objects motion to remain unchanged.
What is the inertial mass?
The inertial mass of an object is the measure of how difficult it is to change the velocity of the object.
What does moment of a force equal?
moment of a force= force x distance
What does a lever do?
A lever transfers the rotational effect of a force- push one end of a lever down and the rotation around the pivot causes the other end to rise.
What does a gear do?
Gears can increase or decrease the speed of rotation and can easily be used to reverse the direction of rotation. They are circular discs that have teeth around the edge.
What objects use levers?
- bicycle hand brakes
- scissors
- pliers
- can opener
What objects use gears?
- Wall clock
- Cars
- Bikes
- Motor bikes
How can you measure reaction time?
You can measure reaction time by doing the dropping ruler test.
What does stopping distance equal?
Stopping distance= reaction distance + braking distance
What is the reaction time?
Reaction distance is the distance the vehicle travels in the drivers reaction time.
What factors effect somebodies reaction time?
- drugs
- alcohol
- tiredness
- distractions
How does speed effect the reaction distance?
The faster a vehicle is going, the further the vehicle will travel during the reaction time.
What is the braking distance?
The braking distance is the distance taken to stop once the brakes have been applied.
What affects the braking distance?
- Your speed
- The mass of the vehicle
- The condition of the brakes on the car
- How good the grips are on the tyres of the car.
What happens when the brake pedal is pushed?
When the brake pedal is pushed, this causes brake pads to be pressed onto the wheels. This contact causes friction, which causes work to be done.
What does energy transferred (work done) equal
Work done= force x distance
What does kinetic energy equal?
kinetic energy= 0.5 x mass x (speed)^2
What does gravitational potential energy equal?
gravitational potential energy= mass x gravitational field strength x height.
What stores are filled and emptied when a ball is thrown in the air?
When a ball is thrown into the air energy is transferred mechanically from the kinetic energy store of the ball to its gravitational potential energy store.
What stores are filled and emptied when a bat hits a stationary ball?
Some energy in the kinetic energy store of the bat is transferred mechanically to the thermal energy stors of the bat, the ball and their surroundings. Some energy is transferred mechanically from the kinetic energy store of the bat to the kinetic energy store of the ball. The rest of the energy is carried away by sound.
What is power?
Power is the rate at which energy is transferred in a system.
What does power equal in terms of energy transferred and time?
Power= energy transferred / time
