Topic 1- Forces And Motion Flashcards
What does the gradient of a distance-time graph represent?
Speed
What does a flat line represent on a distance-time graph?
The object is stationary
What does a steep line represent on a distance-time graph?
A fast speed
What does it mean if a distance-time graph has a curved line?
The object is acceleration or decelerating.
If the curve is steepening= speeding up
If the curve is levelling= slowing down.
Equation for speed
Speed= distance divided by time
Describe an experiment to investigate the motion of everyday objects
1) lay 4X1 metre rules along a surface.
2) push the car and time how long it takes to travel 50cm
3) plot the data on a distance-time graph
4) repeat experiments with different strengths of force.
Equation for acceleration
(Change in velocity) divided by time
What does the gradient of a velocity-time graph represent?
Gradient= acceleration
What does a flat line on a velocity-time graph represent?
A constant speed
What does a steep gradient of a velocity-time graph represent?
A high acceleration/ deceleration
What does the area under a velocity-time graph represent?
Distance travelled
What does a curved gradient of a velocity-time graph represent?
Change in acceleration
What is a force?
A force is something that acts on a body. It can make the object change shape, speed and direction.
What are examples of forces?
Weight, friction, thrust, magnetic etc.
What is a vector quantity
Something that has a magnitude and direction
What is a scalar quantity
Something that only has a magnitude. No direction.
What quantity is a force
A vector quantity
What do unbalanced forces cause and what do balanced forces cause
Unbalanced forces cause an object to accelerate.
Balanced forces will either produce a steady speed or no movement.
What is friction
A force that opposes movement
What is the equation for force
Force= mass X acceleration
Equation for weight
Weight= mass X g
What forces act on a falling object (terminal velocity set out q)
1) At first, the only force acting on the object is its weight so there is a large acceleration downwards. (A big resultant force)
2) As speed increases , so does air resistance.
3) this decreases the resultant force so the object doesn’t accelerates as greatly.
4) eventually drag= speed
5) no unbalanced force= terminal velocity
Describe an experiment to investigate falling objects
1) Collect a bunch of sycamore seeds of similar mass but different wing lengths.
2) drop each seed from the same height (higher the better) and time how long it takes to reach the floor.
3) repeat 3 times for each length and find average.
4) plot graph of time over length of wings.
* the bigger the surface area, the bigger the drag. This means that it will have a lower terminal velocity and so it falls more slowly.
What factors affect stopping distance?
Speed
Mass of car
Reaction time
Road conditions
Equation for momentum
Momentum= mass X velocity
How do car safety features such as seat belts and crumple zones reduce injuries?
They increase the stopping time so that there is a smaller overall force acting on the person.
What is the law of conservation of momentum?
Momentum before= momentum after.
Only if the object has not been acted on by external forces.
Equation for force in terms of momentum?
Change in momentum / time.
What is newtons 3rd law?
F= m X a.
To every action, there is an equal and opposite reaction.
Equation for moments
Moment= force X perpendicular distance from pivot
Where does the weight of the body of an object act through?
It’s centre of gravity.
What happens if you add more weights to a plank of wood.
The pivots pushing up have to exert a larger force in order to balance the new mass
Describe an experiment to see if an object obeys hooke’s law
1) Set up a clamp and stand with a spring and hanging mass. (Have extra weights)
2) measure the length of the spring with no load.
3) add one mass at a time and after it has come to a rest, measure the extension.
4) repeat this for all the loads.
5) once done, repeat and find average.
* plot these results on force-extension graph. If the line is a straight line, then the object obeys hooke’s law.
What is hooke’s law?
The extension of a stretched wire is proportional to its load.
What does it mean if a material is elastic?
It has the ability to recover its original shape after the forces causing its deformation have been removed.
What does it mean if a force-extension graph has a curved line
The object is plastic and has passed its point of elasticity. This means that it is permanently stretched past its original length.
Why is gravitational field strength different on other planets?
This is because different planets have offering masses.
What does gravitational cause things to do?
Moons orbit planets
Planets orbit the sun
Comets orbit the sun
Artificial satellites orbit the Earth.
What are they comets of comets, moons and planets like?
Comets are highly elliptical
Moons and planets are slightly elliptical but assumed to be circular
Equation for orbital speed?
(2 X pi X orbital radius)/ time
What is a universe?
A large collection of galaxies
What are galaxies?
A large collection of billions of stars
Where is our solar system?
In the Milky Way
