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## Homework Statement

A car with mass 2500 kilograms travels along a straight level road at 90 km/h. A headwind begins to blow with a force of 200 N causing the car to slow down. Calculate the car’s deceleration.

## Homework Equations

The book uses the formula F =ma so

**3. Book's solution**

= 0.08 m/s2

My confusion with the calculation comes from not knowing why the speed of the car is not considered. It’s a 2500 kg car driving at 90km/h so must have a force or a momentum that is important. Why is the car's speed not considered?

I need to ask a bit more about the question here please:

__The second part of the question says__

**The car travelling at a steady speed collides with a stationary traffic cone of mass 10 kg. The traffic on accelerates in the direction of the car’s motion at 29 m/s2.**

Calculate the force applied to the traffic cone by the car.

Calculate the force applied to the traffic cone by the car.

Book says: Calculation is F =ma = 10 x 29 = 290N

Book asks: What is the force applied by the cone to the car in the collision (hint in the paper is: Newton’s third law of motion).

Answer in the book is 290N. But shouldn’t the answer be

**-290N**because “to every action is an equal and opposite reaction”.