Topic 1 - Forces and Motion Flashcards
What does the gradient of a distance-time graph represent?
What does zero represent?
What does a Horizontal line represent?
What is a negative gradient?
Gradient = Speed
Zero = The origin - Not moved forward/back at all
Horizontal line = No movement, stationary
Negative Gradient = Returning to start
The equation is (Average) Speed = Distance Moved / Time Taken (S=D/T), but what are the units and rearrangements?
S = D/T
D = SxT
T = D/S
S = Speed (metres/second)
D = Distance (metres)
T = Time (second)
The equation is Acceleration = Change in Velocity / Time Taken (a=△V/t OR a=(v-u)/t), but what are the rearrangements and units?
a = (v-u)/t
t = (v-u)/a
v = t x a + u
u = v - t x a
a = Acceleration (metres/second²)
v = Final velocity (m/s)
u = Original velocity (m/s)
t = Time (s)
△ = Change in…
What does the gradient of a velocity-time graph represent?
What does zero represent?
What does a Horizontal line represent?
What is a negative gradient?
Gradient = (Rate of) Acceleration
Zero = No movement
Horizontal line = A constant speed
Negative Gradient = Deceleration
How do you find acceleration from a velocity-time graph?
Find the gradient, then use a = (v-u)/t to find acceleration
How do you find the distance travelled using a velocity-time graph?
Find the area under the line (by splitting the area into squares, triangles etc) and add them together, that will equal the distance travelled
The equation is Final Speed² = Initial Speed² + (2x acceleration x distance moved)
v² = u² + (2 x a x s)
But what are the units and rearrangements?
v² = u² + (2 x a x s)
u² = v² - (2 x a x s)
a = v² - u² / 2s
s = v² - u² / 2a
v = Final speed (m/s)
u = Initial speed (m/s)
a = Acceleration (m/s²)
s = Distance moved (m)
What is the difference between vector and scalar quantities?
Vectors have a size and direction, scalars have just size
What is the force which opposes motion?
Friction
The equation is force = mass x acceleration (F = m x a), but what are the units and rearrangements?
f = ma
a = f / m
m = f / a
F = Force (N)
M = Mass (kg)
A = Acceleration (m/s²)
The equation is weight = mass x gravitational field strength (w = m x g), but what are the units and rearrangements?
w = m x g
g = w / m
m = w / g
W = Weight (N)
M = Mass (kg)
G = Gravitational field strength (N/kg)
How do you calculate stopping distance?
Thinking distance + Braking distance = Stopping distance
What factors affect thinking distance and braking distance, or both?
What are the forces acting on falling objects (why do falling objects reach terminal velocity)
What is the original diagonal line on a force-extension graph called? What is it associated with?
It is called the linear region and is the area of Hooke’s law where a spring obeys Hooke’s law
What is Hooke’s law?
The stretch of a spring is directly proportional to the weight added, up until the limit of proportionality
The equation for Hooke’s law is f = k x e, but what are the rearrangements and units?
f = k x e
k = f / e
e = f / k
f = Force (N)
k = Spring Constant (N/m)
e = Extension (M)
What is elasticity? What is elastic deformation?
Elasticity is the ability of an object to return to its original shape after deforming forces are removed.
Elastic deformation is when an object returns to its original shape after deforming forces are removed.
The equation for momentum is p = m x v, but what are the units and rearrangements?
p = m x v
m = p / v
v = p / m
p = momentum (kgm/s)
m = mass (kg)
v = velocity (m/s)
What is the conservation of momentum law?
Total momentum before an event = Total momentum after an event
What are the units of F = m△v / △t?
F = Force (N)
m = Mass (kg)
△v = change in velocity (m/s)
△t = change in time / time takes (s)
How do safety features use momentum?
Safety features like seatbelts, air bags or crumple zones all increase the time taken for a collision to occur, therefore reducing the force.
What are the three steps of a safety feature that reduces the risk of injury?
- Increase the time taken to stop
- This decreases the rate of change of momentum
- This will reduce the impact force
What is Newton’s 3rd law, and how does it work?
Newton’s 3rd law os that every force has an equal and opposite force.
It works when two objects hit each other and bounce off each other; they exert a force on each other, just in the opposite direction.
