a car is moving with a uniform speed of 72km/h .The driver sees a child at a distance of 50m. he applies brakes to stop the car just before the child. Calculate the acceleration.
vf^2=vi^2+2ad
solve for a
To calculate the acceleration, we need to first find the time it takes for the car to stop.
Given:
Initial velocity, u = 72 km/h = 72,000 m/60 mins = 1,200 m/min
Final velocity, v = 0 m/min
Distance, s = 50 m
To find the time taken:
The equation of motion we can use is:
v^2 = u^2 + 2as
Substituting the values:
0^2 = (1,200)^2 + 2a(50)
0 = 1,440,000 + 100a
100a = -1,440,000
a = -1,440,000 / 100
a = -14,400 m/min^2
The acceleration of the car is -14,400 m/min^2.
Note: The negative sign indicates that the direction of acceleration is opposite to the direction of car's initial motion.