Equations of motion Flashcards
What is the equation for acceleration?
acceleration (m/s[2]) = change in velocity (m/s) / time taken (s)
a = (v - u) / t
a = acceleration v = final velocity u = initial velocity t = time taken
What is velocity?
The change in distance per second.
What is acceleration?
A change in velocity per second.
What is the equation for velocity?
(final velocity)[2] - (initial velocity)[2] = 2 x acceleration x distance
v[2] - u[2] = 2 x a x x
x is the distance travelled.
v[2] = u[2] + 2ax
Is acceleration vector or scalar?
vector
Is velocity vector or scalar?
vector
A cat changes its speed from 2.5 m/s to 10 m/s over a period of 3 s. Calculate the cat’s acceleration.
v = 10 m/s, u = 2.5 m/s, t = 3 s, a = ?
a = (v - u) ÷ t
a = (10 m/s - 2.5 m/s) ÷ 3 s
a = 7.5 m/s ÷ 3 s
a = 2.5 m/s²
A motorcyclist passes through green traffic lights with an initial velocity of 4 m/s and then accelerates at a rate of 2.4 m/s², covering a total distance of 200 m. Calculate the final velocity of the motorcycle.
u = 4 m/s, a = 2.4 m/s², x = 200 m, v = ?
v² = u² + 2ax
v² = (4)² + 2 x 2.4 x 200
v² = 16 + 960 = 976
v = √976 = 31.2 m/s
A dog changes its speed from 2 m/s to 8 m/s in 5 s. Calculate the acceleration of the dog.
a = (8 m/s - 2 m/s) ÷ 5 s = 6 m/s ÷ 5 s = 1.2 m/s²
An aeroplane starts at rest and accelerates at 1.6 m/s² down a runway. After 1.8 km it takes off. Calculate it’s speed at take-off.
v² - 0² = 2 x 1.6 m/s² x 1800 m = 5760 m²/s; v = √5760 = 75.9 m/s
A car passes through traffic lights at a speed of 5 m/s and then accelerates at 1.2 m/s² until it has reached a final speed of 18 m/s. Calculate the distance it has travelled from the traffic lights.
v² - u² = 2ax, (18 m/s)² - (5 m/s)² = 2 x 1.2 m/s² x x; x = (18² - 5²) ÷ 2.4 = 124.6 m
What is it important to do?
convert units
