Section 1 - Forces and Motion Flashcards
What is the equation for SPEED?
Speed = Distance Moved / Time Taken
In a distance-time graph, how is the speed represented?
The gradient is equal to the speed
In a distance-time graph, what does a curve mean?
Curves represent acceleration or deceleration
What is the equation for ACCELERATION?
Acceleration = Change in Velocity / Time Taken
In a velocity-time graph, how is the acceleration represented?
The gradient is equal to the acceleration
In a velocity-time graph, how is the distance travelled in a certain period of time represented?
The area under any section of the graph is equal to the distance travelled in that time interval
What is the equation for FORCE?
Force = Mass x Acceleration
What is the equation for WEIGHT?
Weight = Mass x Gravitational Field
What are the five main types of forces?
- Gravity or Weight (straight downwards)
- Reaction Force (straight upwards)
- Electrostatic Force (between two charged objects)
- Thrust (speed something up)
- Drag or Air Resistance (slowing things down)
Where does the weight of a body act through?
Its centre of gravity
What is friction?
Friction is a force that opposes motion
Describe an experiment to investigate the motion of a toy car
Set up two light gates. Measure the distance of the two light gates. Allow the car to travel between the two light gates and work out its speed
What are the two forces acting on falling objects?
Drag and Weight
Why do falling objects reach a terminal velocity?
When objects first set off, they have much more force accelerating them than resistance slowing them down. As the velocity increases, the resistance builds up.
This gradually reduces the acceleration until eventually the resistance force is equal to the accelerating force and then it won’t be able to accelerate any more
Describe an experiment using sycamore seeds to investigate the forces acting on a falling object
Time the time taken for a sycamore seed to hit the ground from an assigned height.
You will find out that the longer the wings are, the longer the time taken for it to hit the ground
What is Newton’s Third Law? *
If object A exerts a force on object B, then object B exerts the exact opposite force on object A
What is a vector quantity? *
A vector has size and direction
What is a scalar quantity? *
A scalar only has size
Is force a vector quantity or a scalar quantity? *
it is a vector quantity
How do you find the resultant face of forces that act along a line? *
By adding them end to end
What factors affect vehicle stopping distance?
- Speed - the faster you go, the further it takes to stop
- Mass - the larger the mass, the longer it takes to stop
- Road Condition - the better the conditions, the better
- Reaction Time - the faster, the better
What is the equation for MOMENTUM? *
Momentum = Mass x Velocity
What is the conservation of momentum? *
Momentum is conserved when no external forces act. The total moment after is the same as it was before.
p (1) = p (2)
m (1) x v (1) = m (2) x v (2)
What is the equation for FORCE ACTING? *
Force Acting (N) = Change in Momentum (kg m/s) / Time Taken For Change to Happen (s)
Why do cars have crumple zones, seat belts and air bags? *
Crumple Zones - crumple on impact, increasing the time taken for the car to stop
Seat Belts - stretch slightly, increasing the time taken for the wearer to stop. This reduces the forces acting on the chest.
Air Bags - increase the time taken for the individual to stop.
What is the equation for MOMENT?
Moment (Nm) = Force (N) x Perpendicular Distance (m)
What is the principle of moments? *
If an object is balanced, then total anticlockwise moments is equal to total clockwise moments
If a beam supported by springs has a 10 N weight added in the centre of it, what would the upward force of each spring have to be? *
5 N
Describe an experiment to investigate the relationship between extension and force
Attach a spring to a newton meter and measure its length
Add a 50g weight and measure again
Continue to add another weight and take measurements
Do this up to 400g
By plotting a graph from the results, you can see the extension increases with force; as each time a weight is added, the spring gets longer.
Describe what is happening on a force-extension graph
It starts off linear as it is obeying Hooke’s Law
There is a point where it starts to curve, this is its elastic limit and from then on, the material will be permanently stretched
What is elastic behaviour?
If the material can return to its original shape once the forces are removed
What is gravitational field strength?
Gravitational field strength is how strongly something pulls an object towards it.
Which has a greater gravitational field strength: the Earth or the Moon? How do we know this?
The Earth has a greater gravitational field strength
The pull of the Earth means that we can only jump for a few seconds, but we can jump for a long time on the moon.
What does gravitational force cause?
- Causes moons to orbit planets
- Causes the planets to orbit the sun
- Causes artificial satellites to orbit the Earth
- Causes comets to orbit the sun
What are the differences in the orbits of comets, moons and planets?
Orbits of moons and planets are slightly elliptical
Comets have a very elliptical orbit. They travel fast when they are near to the sun and slower when they are further away.
What is the equation for ORBITAL SPEED?
Orbital Speed = (2 x pi x orbital radius) / time period
What is a universe?
A universe is a large collection of billions of galaxies
What is a galaxy?
A galaxy is a large collection of billions of stars
What is our solar system called?
The Milky Way galaxy
