A particle of mass 0.2 kg is resting in equilibrium on a rough plane inclined at 20° to the horizontal.

1. Show that the friction force acting on the particle is 0.684 N, correct to 3 significant figures.

The coefficient of friction between the particle and the plane is 0.6. A force of magnitude 0.9 N is applied to the particle down a line of greatest slope of the plane. The particle accelerates down the plane.

2. Find this acceleration.