# acceleration of car is required to be calculated

• Sep 15th 2011, 09:36 AM
moonnightingale
acceleration of car is required to be calculated
If a car required 18 seconds to stop to zero speed while it was moving at 50 Km/h, how can we calculate the acceleration or deceleration of car during crash
• Sep 15th 2011, 10:04 AM
e^(i*pi)
Re: acceleration of car is required to be calculated
Quote:

Originally Posted by moonnightingale
If a car required 18 seconds to stop to zero speed while it was moving at 50 Km/h, how can we calculate the acceleration or deceleration of car during crash

$a = \dfrac{v-u}{t}$

You know v, u and t. It is perfectly acceptable for a to be negative.
• Sep 15th 2011, 10:16 AM
moonnightingale
Re: acceleration of car is required to be calculated
the answer coes to be -0.77 m/sec
is it correct
• Sep 15th 2011, 10:30 AM
e^(i*pi)
Re: acceleration of car is required to be calculated
Quote:

Originally Posted by moonnightingale
the answer coes to be -0.77 m/sec
is it correct

EDIT: Your magnitude (-0.77) is correct but your units are not

Remember that acceleration is measured in $\text{m}\cdot \text{s}^{-2}$