Define speed
The rate of change of distance with time
What is the equation for speed?
Speed=distance/time ms-1
Define velocity
The rate of change of displacement with time, where displacement is a distance in a stated direction
What is the equation for velocity?
Velocity= displacement/time ms-1 plus direction v= Δs/Δt
Are displacement and velocity scalar or vector quantities?
Vector; magnitude and direction
How can you find instantaneous velocity graphically?
Draw a tangent at a point and work out the gradient using Δy/Δx
Define acceleration
The rate of change of velocity with time
What is the equation for acceleration?
Acceleration= change in velocity/time ms-2 plus direction a= Δv/Δt OR a= v-u/t
What could a negative acceleration mean?
1) Accelerating backwards (against original direction) 2) Deceleration
How can average acceleration be measured using lab techniques?
Roll a trolley with a interrupter card attached down a ramp, through two separate light gates attached to a data logger. Distance= length of card Time= time in each data logger Calculate the velocity at each light gate then work out acceleration using a=v-u/t TAKE REPEAT READINGS!
How can instantaneous acceleration be calculated using lab techniques?
Roll a trolley with a picket fence interrupter card attached down a ramp, through a light gate attached to a data logger. Distance= length of each ‘picket’ on the card Time= time in each data logger Calculate the velocity at each light gate then work out acceleration using a= Δv/t TAKE REPEAT READINGS!
What are the benefits of using data loggers to record data?
-Synchronous readings -Recordings as exact times -Higher sampling rate -Fewer people needed to complete investigation -Less chance of random error (due to to human reaction time)
Why is random error harder to be accounted for than systematic error.
It is different every time
What are kinematic equations?
Equations used for any object that is accelerating
What does SUVAT stand for?
S-displacement (m)
U-initial velocity (ms-1)
V-final velocity (ms-1)
A-acceleration (ms-2)
T-time (s)
What is the SUVAT equation for final velocity? How is it derived?
V=u+at a= Δv/t ➡️ a=v-u/t ➡️ at=v-u ➡️ v=u+at
What is the SUVAT equation for displacement when you have final velocity? How is it derived?
s=(v+u/2)t average velocity=(v+u/2) and s=dt ➡️(substitution)➡️ s=(v+u/2)t
What is the SUVAT equation for displacement when you don’t have final velocity? How is it derived?
s=ut+1/2at2 s=(v+u/2)t and v=u+at ➡️(substitution)➡️ s=(u+at+u/2)t ➡️ s=t(2u/2 +at/2) ➡️(expansion)➡️ s=ut+q/2at2
What is the SUVAT equation for velocity^2? How is it derived?
V2=u2+2as V=u+at ➡️ v2=(u+at)2 ➡️(expand)➡️ v2=(u+at)(u+at) ➡️ v2=u2+2uat+a2t2 ➡️(factorise)➡️ v2=u2+2a(ut+1/2at2) and s=ut+1/2at2 ➡️(substitution)➡️ v2=u2+as
Name 3 types of motion graphs
Distance-time Velocity-time Acceleration-time
What is the gradient for a distance-time graph?
Velocity= Δs/t
What is the gradient for a velocity-time graph?
Acceleration= Δv/t
What does the area under a velocity-time graph represent?
Distance
What are 3 ways which you can measure ‘g’ by free fall?
-electromagnet/trap door method -light gate method (picket fence is dropped) -multiflash photography
Is speed a scalar or vector quantity?
Scalar; it has magnitude only
How are vectors added in line?
Add same direction and subtract oposite direction
How do you add perpendicular vestors?
Draw a free body diagram and se Pythagoras’ theorem or trigonometry.
How do you add oblique vectors?
Draw a scale diagram (a parallelogram to find the hypotenuse length).
What is a free-body diagram?
A diagram with the object drawn and the forces drawn on.
Define a moment:
A measure of an objects tendency to cause rotation.
What is the equation for a moment?
Moment= Force x Perpendicular distance from pivot to line of action
M (Nm)= F(N) d (m)
Describe an object in rotational equilibrium:
The resultant force acting of it is zero. This is known as the principle of moments which means that the clockwise moment= anticlockwise moment.
Define centre of gravity:
The position where the sum of an objects weight force appears to act from.
How is centre of gravity found for symmetrical objects?
At the intersection of lines of symmetry.
How is centre of gravity found for irregular objects?
Hanging an objects with a plumbob and drawing lines as it falls.
What is Newton’s first law?
If an object is stationary it will stay stationary unless acted on by a resultant force.
If an object is moving at a constant velocity it will stay at that velocity unless acted on by a resultant force.
What is Newton’s second law?
Resultant force= mass x acceleration
F (N) = m (kg) a (ms-1)
What is Newton’s third law?
To every action there is an equal and opposite reaction.
What are 5 differences between Newton’s first and third laws?
1) Forces in Newton I acts on a single object while forces in Newton III act of 2 different objects.
2) Newton I concerns any number of forces while Newton III always concerns only 2.
3) The forces can be different types in Newton I while they must be the same in Newton III.
4) Forces are always equal and opposite in Newton III but they must be two forces on a body in equilibrium for this to occur in Newton I
5) Newton III always applies but Newton I only appies for bodies in equilibrium.
What are the 4 kinds of forces?
Electromagentism
Gravity/ gravitational
Strong force
Subatomic weak force
Define projectile:
A moving object on which the only force of significance acting on it is weight. They are generally thrown and form a pre-determined trajectory based on its initial velocity
What 3 kinds of projectile are there?
Vertical
Horizontal
Oblique
What shape does a horizontal projectile form?
A parabola
How does speed change for horizontal and vertical components of projectiles?
Horizonal projectiles: constant velocity s=vt
Vertical projectiles: accelerating at ‘g’ SUVAT equations
