kinematics of a particle

• May 6th 2009, 06:28 AM
Sundae
kinematics of a particle
Hiya, i have a very simple question! dunno how to work it out so i'd appreciate if someone showed me step by step and explained it.

-A, B and C are three points on a straight road such that AB = 80m and BC = 60m. A car travelling with uniform acceleration passes A, B and C at times t = 0, t = 4s and t = 6s respectively. Modelling the car as a particle find its acceleration and its velocity at A.

-the answers are: 3 1/3 ms^(-2), 13 1/3 ms^(-1)

thx!
• May 6th 2009, 08:23 AM
skeeter
Quote:

Originally Posted by Sundae
Hiya, i have a very simple question! dunno how to work it out so i'd appreciate if someone showed me step by step and explained it.

-A, B and C are three points on a straight road such that AB = 80m and BC = 60m. A car travelling with uniform acceleration passes A, B and C at times t = 0, t = 4s and t = 6s respectively. Modelling the car as a particle find its acceleration and its velocity at A.

-the answers are: 3 1/3 ms^(-2), 13 1/3 ms^(-1)

thx!

note the kinematics equation for uniform acceleration ...

$\Delta x = v_0 \cdot t + \frac{1}{2}at^2
$

two equations can be formed ...

$80 = v_A \cdot 4 + \frac{1}{2} a (4)^2$

$140 = v_A \cdot 6 + \frac{1}{2} a (6)^2
$

two equations, two unknowns ... solve the system.
• May 6th 2009, 12:13 PM
Sundae
Thx alot!