A car of mass 1200kg travelling @ 72 km/h is brought to rest in 4s.Find a) the average deceleration b)the average braking force
a) 72 km/h = 20 m/s
Deceleration = 20/4 = 5 m/s^2
b) Momentum change = Avg. Force * Time
Solve for the Average Force
15000N
A 5m\s B 6000
Deceleration =5m/s^2
Force=6000N
72km/h=20m/s
20/4
=5m/s
To find the average deceleration, we can use the formula:
acceleration = (final velocity - initial velocity) / time
a) The car is brought to rest, so the final velocity is 0 km/h. However, we need to convert the initial velocity from km/h to m/s.
1 km/h is equivalent to 0.2778 m/s. Therefore, the initial velocity is (72 km/h) x (0.2778 m/s) = 20 m/s.
Plugging in the values into the formula, we get:
acceleration = (0 - 20 m/s) / 4 s = -5 m/s^2
The negative sign indicates that the car is decelerating.
b) To find the average braking force, we can use Newton's second law of motion:
force = mass x acceleration
The mass of the car is given as 1200 kg, and the average deceleration is -5 m/s^2 (negative because decelerating).
Plugging in the values into the formula, we get:
force = 1200 kg x (-5 m/s^2) = -6000 N
Again, the negative sign indicates that the force is in the opposite direction of motion, which signifies braking force.
a) Deceleration is -5
b) Average braking force -6000