1 km/hr = 20 m/s
periods are not measured in m/s
a = (-20m/s)/(4s) = -5 m/s^2
F = ma
s = 1/2 at^2
...
A car of mass 1200kg travelling at 72km/h was brought to rest in 4 seconds.
1. what is this period in m/s?
2. find;
a. the deceleration of the car.
b. the force that caused the car to come to rest.
c.the distance it travelled during its deceleration.
5 answers
1. 72km/h = 72000m/3600s = 20 m/s.
2a. V2 = V1 + a*t.
0 = 20 + a*4,
a = -5 m/s^2 = deceleration.
2b. F = M*a = 1200 * (-5) = -6000 N.
The negative sign means the force opposes the motion.
2c. V2^2 = V1^2 + 2a*d.
0 = 20 - 10d,
d = 2m.
2a. V2 = V1 + a*t.
0 = 20 + a*4,
a = -5 m/s^2 = deceleration.
2b. F = M*a = 1200 * (-5) = -6000 N.
The negative sign means the force opposes the motion.
2c. V2^2 = V1^2 + 2a*d.
0 = 20 - 10d,
d = 2m.
2c. Correction:
0 = 20^2 - 10d,
d = 40 m.
0 = 20^2 - 10d,
d = 40 m.
12
what is physics
4 answers