Physics 1 - Work, Energy and Power Flashcards
1.2P List the units and unit symbols for: moments
Newton Metre (Nm)
1.2P List the units and unit symbols for: momentum
Kilogram metre per second (kg m/s)
1.3 Plot a distance-time graph for the following motion: stationary, constant speed, acceleration, deceleration
SEE ONENOTE Stationary - horizontal line Constant speed - straight line Acceleration - gradient increasing Deceleration - gradient decreasing
1.3 Describe how speed can be determined from a distance-time graph
Find the gradient
Average speed
Change in distance/change in time
1.4 Write down another equation for average speed if acceleration is constant in words and symbols
average speed=1/2(initial speed+final speed)
1.5 Practical: Describe a generic experiment to determine the average speed of an object
Get a set distance and measure it (ruler, tape measure, trundle wheel)
State how you will measure the time (stopwatch, light gates etc)
State the method (self explanatory)
Repeat, remove anomalies and take an average
Calculate the average speed
1.7 Plot a velocity-time graph for the following motion: stationary, constant speed, acceleration, deceleration
Stationary - Horizontal line on zero
Constant speed - horizontal line
Acceleration - Straight diagonal line going upwards
Deceleration - Straight diagonal line going downwards
1.8 Describe how acceleration can be determined from a velocity-time graph
Calculate the gradient
1.9 Describe how distance/displacement travelled can be determined from a velocity-time graph
Calculate the area from the x axis to the line.
Above the axis is a positive displacement, vice versa.
1.10 Write down the equation relating final speed, initial speed, acceleration and distance moved in words and symbols
Final speed squared = initial speed squared + (2 x acceleration x distance)
v^2 = u^2 + 2as
1.11 Describe the possible effects of forces between bodies
Change speed, shape or direction
1.13 State how a vector quantity is different from a scalar quantity
A scalar has only magnitude, a vector has magnitude and direction
1.15 Describe how to calculate the resultant force of several forces acting along a line
Choose one direction to be positive and the other negative. Add the quantities together using the signs used
Is force a scalar or vector?
Vector
1.16 Define friction
A force that opposes motion
1.17 Write down the relationship between unbalanced forces, mass and acceleration in words and symbols
Resultant force = mass x acceleration
∑F=ma
1.19 Define the thinking distance and braking distance
Thinking distance: distance travelled between spotting the hazard and pressing the brakes
Braking distance: distance travelled between pressing the break and coming to a complete stop
1.19 Define stopping distance
Thinking distance + braking distance
1.20 Describe and explain the factors that affect thinking distance
Speed - travel further in the same amount of time
Reaction time - affected by alcohol, tiredness, distraction from phone
1.20 Describe and explain the factors that affect braking distance
Mass - increases momentum and KE
Road/car conditions - reduces braking force
Speed - has greater kinetic energy so takes longer to come to a complete stop
1.21 Describe and sketch the forces acting on a falling object
Weight - downwards
Drag/air resistance/friction - upwards (smaller)
1.21 Define terminal velocity and sketch a diagram
Forces reach equilibrium - drag = weight
Therefore the object travels at a constant speed
- 22 Practical: Design an experiment to investigate how extension varies with applied force for
a. Helical springs
b. Metal wire
c. Rubber band
Set up a clamp, attached to the table by another clamp, with a ruler set upnext to a spring.
Measure the initial length of the spring, then add different masses (IV) and measure the extension (DV)
Accuracy - make sure the ruler is close to avoid a parallax error. Repeat the experiment and calculate an average extension
Plot a force extension graph; put a straight line through it - the gradient is the spring constant.
Wire: do the same but use a micrometre
Rubber band: measure the extension as masses are removed to show the hysteresis in the graph
1.23 Sketch a force-extension graph for a helical spring, metal wire and rubber band and label Hooke’s law region, elastic behaviour, plastic behaviour
Linear part = Hooke’s law region, elastic behaviour
Non linear = plastic behaviour
1.23 State Hooke’s law, and put as an equation
The extension of the material is proportional to the force applied
Force = k (spring constant) x (extension)
1.24 Describe elastic behaviour
The ability to recover its original shape after forces of deformation have been removed
1.25P Write down the relationship between momentum, mass and velocity in words and symbols
Momentum = mass x velocity p = mv
1.27P State the law of conservation of momentum
The total momentum before a collision = total momentum after a collision
- 27P Write down the momentum equation for
a. Two objects colliding and separating
b. Two objects colliding and sticking
c. Two objects separating due to an explosion
m_1 u_1+m_2 u_2=m_1 v_1+m_2 v_2
m_1 u_1+m_2 u_2=(m_1+m_2)v
0=m_1 v_1+m_2 v_2
1.28P Write down the equation for resultant force (impulse) in terms of momentum and time taken in words and symbols
Resultant net force = change in momentum/time taken
∑F=(mv−mu)/t
F=Δp/t
1.26P Describe and explain how safety features work during a collision using the idea of momentum
Change in momentum remains the same but increasing the time taken reduces the impulse (net force).
Seat belt, crumple zones and airbags all increase the time over which there is a change in momentum (F = Δp/t)
1.29P Write down Newton’s 3rd law
If Object A applies a force on Object B, B applies a force on A that is:
Equal in magnitude
Opposite in direction
Same fundamental force
Along the same line
1.30P Write down the relationship between the moment of a force, force and perpendicular distance from a pivot in words and symbols
the turning moment of a force=force×perpendicular distance to pivot
M=F×d
1.31P State where the weight of an object, such as a rod, can be considered to act from
The centre of gravity of the object
1.32P State the principle of moments
When an object is in equilibrium, the sum of the clockwise moments is equal to the sum of the anti-clockwise moments
1.32P Describe how to use the principle of moments with several parallel forces acting on an object
Calculate the clockwise moments Calculate the anti-clockwise moments clockwise moments=anti−clockwise moments Remember also that the vertical and horizontal forces are also balanced, therefore force to the left=forces to the right upwards forces=downwards forces
1.33P Describe how the upwards force generated by two pivots supporting a beam is affected by the position of a heavy object placed on the beam
The support closest to the mass provides the greater upwards force
As the object moves to the other one, the force decreases for the closer one and increases for the one the object’s getting closer to
