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What force is required to accelerate a car weighing 20,000 N from 30.0km/h to 70.0km/h in 10sec?
Force = Mass x Acceleration
Acceleration = Change in Velocity / Time taken
Change in Velocity = Final Velocity - Initial Velocity
Now, let's make sure everything is in SI units.
Initial Velocity = 30 x 1000/3600 = 8.33 m/s
Final Velocity = 70 x 1000/3600 = 19.44 m/s
Acceleration = (19.44 - 8.33)/10 = 1.11 m/s²
Mass = Weight / g = 20000/9.81 = 2039 Kg
Force = ma = 2039 x 1.11 = 2265 N
Hence, the force required is 2265 N.
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Fahim Ur Rehman
Answered May 30, 2017
First you need to convert the units, its your choice whether you convert the velocities from km/h to m/s or or convert the time from s to h.
V1= 30km/h= (30 x 1000) / 3600= 30000 / 3600= 8.33 m/s
V2= 70km/h= (70 x 1000) / 3600= 70000 / 3600= 19.44 m/s
OR
t= 10s= 10 / 3600= 0.0027= 2.7 x 10^-3 hours
I’m taking velocities
F= ma
but m and a are not given
so m= W/g= 20000 / 9.8= 2040.81 Kg
and a= V/t= (V2 - V1) / t= (19.44 - 8.33) / 10= 11.11 / 10= 1.111 m/s^2
now F= ma= 2040.81 x 1.111= 2267.34 N
2267.34 N are required to accelerate the car weighing 20000 N from 30 Km/h to 70 Km/h.
