Phy (F.4 )

A sports car accelerates along a straight line from rest at a rate of 6ms-2 for 4s and then its acceleration changes to -4ms-2 foe 2s .

(a) Find the maximum speed of the car . Express the answer in kmh-1.

(b)Find the final speed of the car.Express the answer in kmh-1

(c)Find the average acceleration of the car. Express the answer in ms-2

2 Answers

Rating
  • MARCO
    Lv 7
    1 decade ago
    Favorite Answer

    The above equations are right ,but he still had not changed the answer for question(1)and (2) to kmh-1

    (a) Find the maximum speed of the car . Express the answer in kmh-1.

    First we have the following equation:

    v=u+at

    V is the maximum speed of the car, u is the initial speed of the car, a is the acceleration, and t is the time

    as the starting speed is 0, so u=0

    v=u+at

    v=0+(6)(4)

    v=24ms-1

    v=24/1000*60*60

    = 86.4km -1

    so the maximum speed is 86.4km -1

    ________________________________

    (b)Find the final speed of the car.Express the answer in kmh-1

    after reaching the maximum speed of v=24ms-1,it started to decelerate:

    v=u+at

    v=24+(-4)(2)

    v=16ms-1

    =16/1000*60*60

    =57.6kmh-1

    so the final speed is 57.6kmh -1

    ______________________________

    c)Find the average acceleration of the car. Express the answer in ms-2

    a=Δv/Δt

    a=(final speed-initial speed)/(time taken over the movement)

    a=(16 -0)ms-1/(4+2)s

    a=2.67ms-2

    so the average acceleration of the car is 2.67ms-2

  • 1 decade ago

    (a) v=u+at

    v=0+6*4

    v=24ms-1

    v=24*3600/1000 kmh-1

    v=86.4kmh-1

    (b) v=u+at

    v=24+(-4)(2)

    v=16ms-1

    v=16*3600/1000 kmh-1

    v=57.6kmh-1

    (c)v=u+at

    16=0+6a

    a=2.67ms-2 (to 3 sig. fig.)

    Source(s): calculator
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