A car of mass 1000kg travelling @72km/hr is brought to rest in a distance of40m find average stoping for nd time taken
I don't understand were you get 40
What what is the formular for retardation
To find the average stopping force and the time taken to bring the car to rest, we can use the equations of motion.
First, let's convert the velocity from km/hr to m/s:
Given velocity = 72 km/hr
Converting to m/s: 72 km/hr * (1000 m/km) / (3600 s/hr) = 20 m/s
Now, let's calculate the average stopping force:
The average stopping force can be found by using Newton's second law of motion, which states that force (F) is equal to mass (m) multiplied by acceleration (a). In this case, the acceleration is the change in velocity divided by the time taken (t).
Initial velocity (u) = 20 m/s
Final velocity (v) = 0 m/s (car is at rest)
Distance traveled (s) = 40 m
We know that the formula to calculate acceleration (a) is:
a = (v - u) / t
Since the car is being brought to rest, v = 0, and the equation can be rearranged to solve for time (t):
t = (v - u) / a
Substituting the values:
t = (0 - 20) / a
To find acceleration (a), we can use another equation of motion:
v^2 = u^2 + 2as
Rearranging the equation to solve for acceleration (a):
a = (v^2 - u^2) / (2s)
Substituting the values:
a = (0 - (20)^2) / (2 * 40)
Calculating the value of 'a':
a = -400 / 80
a = -5 m/s^2 (The negative sign indicates deceleration)
Now, substitute the value of acceleration (a) back into the equation to find the time taken (t):
t = (0 - 20) / (-5)
t = 4 seconds
Therefore, the average stopping force is not calculated in this question. The time taken to bring the car to rest is 4 seconds.
Vo = 72km/h = 72000m/3600s = 20 m/s.
V^2 = Vo^2 + 2a*d = 0.
20^2 + 2a*40 = 0.
a = -5 m/s^2.
V = Vo + a*t = 0.
20 + (-5)t = 0,
t = 4 s. = stopping time.
about 20 meters/second initial speed
mass not relevant
speed at end = original speed + a t
a t = 0 - 20
t = -20/a (Note a is negative of course)
distance = Vi t + 0.5 a t^2
40 = 20 (-20/a) +(0.5) (a) (-20/a)^2
40 = -400/a + 200/a = -200/a
a = -200/40 = -5 m/s^32
t = -20/-5 = 4 seconds
check my arithmetic