Summary Physics ch4
4.1 Accelerating and decelerating
Acceleration, uniform acceleration, uniform motion, deceleration, uniform deceleration.
(v,t) diagram= a speed time diagram. X axis is time and Y axis velocity. (used by calculating distance)
(x,t) diagram= a position time diagram. X axis is time and Y axis position.
In a (v,t)-diagram, the surface area underneath a curve determines the distance traveled.
Vavg= distance in meters(s) ÷ time in seconds(t). If in km/h, answer times 3.6
When the graph isn’t easy to read because it is curved you estimate the distance by counting squares.
v final−v initial
a= , answer in m/s2
t final−t initial Fr
∆v W
a= , ∆ v=a ∙ ∆ t , ∆ t=∆ v ÷ a
∆t es
4.2 Force, mass and acceleration
a m
The total sum of forces on an object is
equal to mass x acceleration
Fres = m ∙ a, a = Fres : m, m = Fres : a
∆
The larger an objects mass is, the more force you must v
exert to change its velocity.
∆
Fg = m ∙ g s
t
4.3 Forces and work
Producing a force requires energy. We call this energy ‘work’
W=F∙s
For energy we simply use the joule (J).
Power is defined the energy consumed in a certain time, thus for mechanical power. And we use as unit W.
W
Pused=
t
1 horsepower corresponds to 735.75 W.
Energy can never be created nor destroyed. It can only be converted from one form to the other.
To graphically show these conversions, we employ so called ‘energy-flow diagrams’.
The degree to which a device uses energy in a useful manner is known as the efficiency of the device.
E used
η= ∙100 % Heat energy (70%)
E total Chemical energy
W = Eused`, it is the same. (100%)
Etotal is mostly the liters of Mechanical energy (30%)
gas you use times the amount of joules 1 liter consists of.
4.4 Braking and collisions
Stopping distance= reaction distance(reaction time) + braking distance
The faster someone is driving, the greater the reaction distance is.
Ways to reduce the deceleration; Reduce the collision speed (decrease ∆v), Enlarge the collision time
(increase ∆t)
Enlarging collision time; Crumple zone (compresses front and back of car instead of compressing you), Seat-
belt (increases stopping distance, thus increasing ∆t)
a
G-force ¿
g
4.1 Accelerating and decelerating
Acceleration, uniform acceleration, uniform motion, deceleration, uniform deceleration.
(v,t) diagram= a speed time diagram. X axis is time and Y axis velocity. (used by calculating distance)
(x,t) diagram= a position time diagram. X axis is time and Y axis position.
In a (v,t)-diagram, the surface area underneath a curve determines the distance traveled.
Vavg= distance in meters(s) ÷ time in seconds(t). If in km/h, answer times 3.6
When the graph isn’t easy to read because it is curved you estimate the distance by counting squares.
v final−v initial
a= , answer in m/s2
t final−t initial Fr
∆v W
a= , ∆ v=a ∙ ∆ t , ∆ t=∆ v ÷ a
∆t es
4.2 Force, mass and acceleration
a m
The total sum of forces on an object is
equal to mass x acceleration
Fres = m ∙ a, a = Fres : m, m = Fres : a
∆
The larger an objects mass is, the more force you must v
exert to change its velocity.
∆
Fg = m ∙ g s
t
4.3 Forces and work
Producing a force requires energy. We call this energy ‘work’
W=F∙s
For energy we simply use the joule (J).
Power is defined the energy consumed in a certain time, thus for mechanical power. And we use as unit W.
W
Pused=
t
1 horsepower corresponds to 735.75 W.
Energy can never be created nor destroyed. It can only be converted from one form to the other.
To graphically show these conversions, we employ so called ‘energy-flow diagrams’.
The degree to which a device uses energy in a useful manner is known as the efficiency of the device.
E used
η= ∙100 % Heat energy (70%)
E total Chemical energy
W = Eused`, it is the same. (100%)
Etotal is mostly the liters of Mechanical energy (30%)
gas you use times the amount of joules 1 liter consists of.
4.4 Braking and collisions
Stopping distance= reaction distance(reaction time) + braking distance
The faster someone is driving, the greater the reaction distance is.
Ways to reduce the deceleration; Reduce the collision speed (decrease ∆v), Enlarge the collision time
(increase ∆t)
Enlarging collision time; Crumple zone (compresses front and back of car instead of compressing you), Seat-
belt (increases stopping distance, thus increasing ∆t)
a
G-force ¿
g
