Calculating Force Required to Overcome Resistance of Road & Wind at 75.0km/hr

In summary, the resistance of the road and wind against the movement of the car at a speed of 75 km/hr is approximately 63% of the total output power of 69 HP. Converting 75 km/hr to SI units of m/s is necessary to calculate the force using the formula of power=force x distance/time.
  • #1
jacksondwrd
2
0
You are testing a new car in a wind-tunnel for road and wind resistance. At a speed of 75.0 Km/hr you have found that 63.0 % of the total output power of an automobile engine is used in overcoming the resistance of the road and wind against the movement of the car. If the output power of a particular car engine is 69.00 HP, what is this resistance (ie. what is the force)? Give your answer in Newtons. (Take one HP as 746 Watts.


so i was like calcualting it like this

69HP=51474
and 60% of 51474 is 32428.62

then i did the formula of the power

power=forcexdistance/time

and got that answer but it is wrong

can anyone explain to me what i did wrong here
 
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  • #2
I am guessing you did not convert your 75 km/hr in SI units m/s. If you didn't, you won't get your answer in Newtons.
 

1. What is the formula for calculating the force required to overcome resistance of road and wind at 75.0km/hr?

The formula for calculating force required to overcome resistance of road and wind at 75.0km/hr is F = 0.5 * p * v^2 * Cd * A, where F is the force, p is the air density, v is the velocity, Cd is the drag coefficient, and A is the frontal area.

2. How do the road and wind conditions affect the force required to travel at 75.0km/hr?

The force required to travel at 75.0km/hr is affected by the road and wind conditions as they create resistance against the vehicle. A rougher road surface or a headwind will increase the resistance, therefore requiring a higher force to maintain the speed of 75.0km/hr.

3. What units should be used for each variable in the force calculation formula?

The units for force should be in Newtons (N), air density in kilograms per cubic meter (kg/m^3), velocity in meters per second (m/s), drag coefficient is unitless, and frontal area in square meters (m^2).

4. Is the force required to overcome resistance of road and wind at 75.0km/hr the same for all vehicles?

No, the force required to overcome resistance of road and wind at 75.0km/hr will vary for different vehicles depending on their size, shape, and aerodynamic design. For example, a smaller and more streamlined vehicle will require less force compared to a larger and less aerodynamic vehicle.

5. How can the force required to overcome resistance of road and wind at 75.0km/hr be minimized?

The force required to overcome resistance of road and wind at 75.0km/hr can be minimized by reducing the factors that contribute to resistance. This can include using smoother tires, maintaining proper tire pressure, keeping the vehicle clean and free of unnecessary drag, and driving at a steady speed without frequent acceleration and braking.

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