Heidi T. answered • 09/01/19
MS in Mathematics, PhD in Physics, 7+ years teaching experience
The first thing that you must do is get consistent units in your problem. time is given in seconds and the acceleration due to gravity is given in meters per second, so need to convert the speed of the car to meters per second.
v = (50 km/hr)(1000 m/km)[(1 hr)/(3600 s)] = 13.9 m/s
(a) Apply the definition of acceleration: acceleration = [change in velocity] / [time over which change occurs] = (0 - 13.9 m/s) / (0.18 s) = - 77.2 m/s2 (in this case you can use the absolute value; the minus sign tells you that the car is slowing down - the acceleration is opposing the motion)
(b) Divide the acceleration by the value for g:
(77.2 m/s2) / (9.8 m/s2) = 7.9
The acceleration experienced during the accident is nearly 8 times greater than the acceleration due to gravity.
Heidi T.
9.8 m/s^2 is the acceleration due to gravity. It is used because you are trying to relate the acceleration in the accident to the acceleration due to gravity. Sometimes 10 m/s^2 is used for the acceleration due to gravity, but it is less accurate.09/04/19
Stephany B.
Where did the 9.8 m/s^2 come from?09/04/19