Module 3 Flashcards
(26 cards)
What is the SUVAT equation for displacement, initial velocity, final velocity and acceleration?
v^2 = u^2 + 2as
What is the SUVAT equation for initial velocity, final velocity, acceleration and time?
v = u + at
What is the SUVAT equation for final velocity, acceleration, time and displacement?
s = vt - 0.5at^2
What is the SUVAT equation for acceleration, time, displacement and initial velocity?
s = ut + 0.5at^2
What is the SUVAT equation for time, displacement, initial velocity and final velocity?
s = 0.5(u + v)t
Explain how to derive the equation ‘s = 0.5(u + v)t’:
On a velocity-time graph, the area underneath is equal to the displacement (s). The area, forming a trapezium, has the area of 0.5(base + base) height, where in this context the height is time (t) and the two bases are initial and final velocity (u and v).
Explain how to derive v = u + at:
On a velocity-time graph, the gradient of the line is equal to the acceleration, and the gradient is equal to the change in y over the change in x. On this graph, the change in y is equal to v - u and change in x is the time. As a = (v - u) / t, then v - u = at and v = u + at.
Define the difference between velocity and speed:
Velocity is a vector quantity (derived from displacement over time) and speed is a scalar quantity (derived from distance over time). For example, when speed is 0 m/s an object is not moving but when velocity is 0 m/s an object can still be moving.
Define the difference between average speed and instantaneous speed:
Instantaneous speed is the speed measured over a very short period of time (by drawing a tangent to a displacement-speed graph). Average speed is measured over a long period of time (e.g: the object can be travelling faster than the average and slower than the average).
Explain thinking, braking and stopping distance:
Thinking distance is the distance travelled in the time taken between the driver seeing an obstacle/reason to brake and actually hitting the brake. The braking distance is the distance travelled in the time taken between the brakes being applied and the vehicle actually stopping. The stopping distance is the combination of these two.
What factors affect stopping distance?
Thinking Distance: tiredness, alcohol, distractions (e.g: phone calls)
Stopping Distance: brake conditions
Both: weather, tires, road surface
What is Newton’s first law?
A body will remain at rest or move with a constant velocity unless it is acted on by a net external force.
What is Newton’s second law?
The rate of change of momentum of an object is directly proportional to the resultant force acting on it.
What is Newton’s third law?
When body A exerts a force on body B, body B exerts an equal and opposite force along the same line on body A, and both forces are the same type.
What is the difference between mass and weight?
Weight of an object is the gravitational force acting on it (and is therefore dependent on the gravitational field strength, which is 9.81 in the case of earth).
Define the equation linking resultant force, mass and acceleration:
Define the equation linking weight, mass and gravitational field strength:
F = ma W = mg
Explain density (include its equation):
Density is a measure of how much mass is contained in a given unit volume. p = m / V
What is the equation of pressure (include its unit)?
Pressure, measured in pascals (Pa), has the equation p = F / A, where F is the force normal (perpendicular to) to the area (A).
Explain the effects of pressure in liquids and the forces involved in relation to objects in equilibrium:
Pressure in a liquid acts in all directions. For an objects in equilibrium, the force upward must equal the weight downward, and therefore the upthrust allowing an objects to float is equal to the downward acting force.
What is Archimedes Principle?
The weight of the fluid displaced by an object is equal to the upthrust of the liquid on the object.
What is the relation between thinking distances at different speeds and braking distance at different speeds?
Thinking distance increases proportionally as the speed of an object increases (3 metres per 10mph increase). On the other hand, braking distance has no proportional increase as speed increases.
What factors affect terminal velocity?
If the object has a more streamlined shape then it will have a higher terminal velocity (as there will be less drag)
The viscosity of the fluid which the object is travelling through decreases the terminal velocity as the fluid becomes more viscous (thicker).
Describe the motion of a parachuter between jumping out of a plane to landing in terms of the forces acting on them and terminal velocity:
When the parachuter jumps out of the plane they begin to accelerate due to their weight, initially at 9.81 m/s^2 towards earth but the rate of acceleration decreases as air resistance (opposing motion) increases. As speed increase so too does the opposing air resistance until the forces are balanced and the object does not accelerate as air resistance is equal to the weight, hence reaching terminal velocity.
What is the effect of the forces that act on an object in equilibrium?
Regardless of the forces, an object in equilibrium will have a resultant force of zero acting on it and the resultant moment acting will be zero.
