## Forces and Acceleration

When a particle experiences resultant forces, it undergoes an acceleration. The acceleration can take more than one form. The particle may speed up, slow down or change direction. In all of these cases we can use Example: A car of mass 1200 kg travels on a horizontal straight road with constant acceleration a) Given that the car’s speed increases from to while travelling a distance of 525 m find the value of b) The car’s engine exerts a constant driving force of 900 N. The resistance to motion of the car is constant and equal to R. Find R.

a) b)  Example: A car of mass 1200 kg is travelling on a horizontal straight road and passes through a point A with speed The power of the car’s engine is 18 kW and the resistance to the car’s motion is 900 N.

i) Find the deceleration of the car at A.

ii) Show that the speed of the car does not fall below while the car continues to move with the engine exerting a constant power of 18 kW.

I) We need to find the maximum force that can be exerted by the car's engine at a speed of We use the equation  The resultant for is 720-900=-180 ii)The resistance to motion is a constant 900 N When the car is travelling at a constant speed all the power supplied by the car's engine must be used to overcome the resistive force to motion.   