A car rolling down a hill accelerates from rest to 22m/s in 40s. What is the average velocity of the car? What is the displacement of the car as it rolls down the hill?

1 Answer
PJ
Jul 6, 2018

#v_("average")= 11ms^(-1)#

#d= 440m#

Explanation:

The car is rolling down a hill so the acceleration is constant.
This is because acceleration due to gravity is constant, so the acceleration of the car on a given slope will be constant (assuming the slope of the hill is constant and ignoring friction).

equations we know:

  1. #v_("average")=(Delta d)/ (Delta t)#
  2. #v_("average")= (v_1-v_0)/2# (where #a# is constant)
  3. #a_("average")=(Delta v)/ (Delta t) #
  4. #d=v_("average")*t#
  5. #d=v_0 t+1/2at^2# (where #a# is constant)
  6. #Delta v = (v_1-v_0) = 22-0 = 22ms^(-1)#
  7. #Delta t =40s#

we know that the car accelerates from #0 to 22ms^(-1)# in 40s so choosing eqn2 and eqn4. :

#v_("average")= (22-0)/2 = 11ms^(-1)#

#d=11ms^(-1)*40s = 440m#

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