COMPOSICIÓ DE COMPOSICIÓ DE MOVIMENTSMOVIMENTS

MRU + MRUMRU + MRU

MRU + MRUAMRU + MRUA

COMPOSING MOTIONS

MRU + MRUMRU + MRUBoat crossing a riverBoat crossing a river

A boat is crossing a river in order to reach the pub on the A boat is crossing a river in order to reach the pub on the opposite side. The velocity of the stream is 2 m/s and the opposite side. The velocity of the stream is 2 m/s and the boat moves 3 m/s fast. If the river is 30 m wide,boat moves 3 m/s fast. If the river is 30 m wide,

a) How long does it take to cross the river?a) How long does it take to cross the river?

b) How far from the pub is the boat reaching the opposite b) How far from the pub is the boat reaching the opposite side?side?

c) How many meters is the total motion of the boat?c) How many meters is the total motion of the boat?

PUB MUR

30

m

Vx= 2 m/s

Vy= 3 m/s

a=0 → MRU y = yo + vy·t

a=0 → MRU x = xo + vx·t

X=20 m

MRU + MRUAMRU + MRUA

Parabolic MotionParabolic Motion A football player shoots the ball at a velocity of 20 A football player shoots the ball at a velocity of 20 m/s and 60º is the initial angle to the horizontal. m/s and 60º is the initial angle to the horizontal. Calculate the maximum height obtained by the ball, Calculate the maximum height obtained by the ball, the total time the ball will be on the air and the range the total time the ball will be on the air and the range (the horizontal distance traveled).(the horizontal distance traveled).

60º

Vo=20 m/s

Vxo = Vo·cos 60

Vyo = Vo·sin 60

a=0 → MRU vxo = vx

x = xo + vx·t

a=g → MRUA vy = vyo + g·t y = yo + vyo·t +

½·g·t2

Help!Maximum height

when Vy = 0

Help!Touches the

ground when y = 0