physics

a car accelerates from rest at a constant rate 'a' for some time. after which it decelerates at a constant rate'b' and comes to rest. if the total time elapsed is t second, evaluate
1) the maximum velocity reached and
2) the total distance travelled.
the answer for this problem is
1) abt/a+b
2) abt^2/2(a+b)
pls tell me how this answer is arrived at

  1. 👍 0
  2. 👎 0
  3. 👁 38
  1. Your given answer for (2) can't be correct, it doesn't have units of distance (it has units of acceleration).

    1. 👍 0
    2. 👎 0
    posted by CANTIUS
  2. In general, v = v_0 + a t, where a is any acceleration.
    Let t1 be the time during the acceleration and t2 be the time during the deceleration and v = the speed at the end of the acceleration.
    v - 0 = a t1
    0 - v = -b t2
    v = a t1 = b t2
    This yields the equation
    a t1 - b t2 = 0
    We also know that
    t1 + t2 = t
    These are two linear equations in two unknowns. There are several ways of solving these. One way is to solve the first equation for t2 in terms of t1, then plug this into the second equation:
    t2 = (a/b)t1
    t1 + (a/b)t1 = t
    (b + a)/b t1 = t
    t1 = b/(a + b) t
    Similarly, t2 = a/(a + b) t
    From one of the first equations
    v = a t1 = a[b/(a + b) t] = abt/(a+b)

    As I mentioned in an earlier comment, your answer for (2) cannot be correct.

    1. 👍 0
    2. 👎 0
    posted by CANTIUS

Respond to this Question

First Name

Your Response

Similar Questions

  1. physics

    a car accelerates from rest at a constant rate alpha for some time, after which it decelerates at a constant rate beeta and comes to rest. if the total time elapsed is t, the maximum velocity acquired by the car will be?

    asked by aman verma on August 15, 2014
  2. physics

    A car and a motorcycle start from rest at the same time on a straight section of the road. However, the motorcycle starts 29.6 m behind the car. The car accelerates at a uniform rate of 3.9 m/s^2 while the motorcycle accelerates

    asked by Alex on December 2, 2009
  3. physics

    A car accelerates from rest at a constant rate A for some time after which it retards at a constant rate B to come to rest. If the time elapsed is T second,calculate the maximum velocity reached?(please try solving this problem by

    asked by help me out it's urgent on September 30, 2012
  4. physics

    A car accelerates from rest at a constant rate A for some time after which it retards at a constant rate B to come to rest. If the time elapsed is T second,calculate the maximum velocity reached?(please try solving this problem by

    asked by help me out it's urgent on September 30, 2012
  5. Alam

    a car accelerates from rest at a constant rate x for some time after which it decelaretes at a constant rate y to come to rest .if the total time elapsed is t the total distance travlled by the car is given by what ?

    asked by Aminur on March 28, 2016
  6. physics

    a car accelerates from rest at a constant rate 'a' for some time. after which it decelerates at a constant rate'b' and comes to rest. if the total time elapsed is t second, evaluate 1) the maximum velocity reached and 2) the total

    asked by pavatharani on July 13, 2011
  7. physics

    A car accelerates from rest at a constant rate of 2.2 m/s2 for 6.9 s. How far does the car travel in this time?

    asked by Steven on October 3, 2011
  8. AP Physics

    1. A car is traveling down the road at a constant speed of 11 km/h. At time zero it is forced to stop. The driver slams on the brakes and the car travels 18 m as it uniformly accelerates, coming to a stop. The car remains at rest

    asked by ThinkPink on September 8, 2011
  9. Physics

    A car starts from rest and accelerates at a constant rate of 1.1 m/s2. If the radius of the car wheels is 29 cm, and the final angular speed of the car wheel is 48 rad/s, how far does the car travel

    asked by Sufian Syed on October 18, 2010
  10. Physics for life science

    1. A car starts from rest and accelerates at a constant rate to 80km/h in 6s in positive direction. What is the acceleration? 2. After how long will the car speed be 120km/h if it keep accelerating at the same rate as in 1.?

    asked by Simeon on March 23, 2010

More Similar Questions