Question

A mass M slides upward along a rough plane surface inclined at angle to the horizontal. Initially the mass has a speed V before it slides a distance Lup the incline. The coefficient of kinetic friction between the mass and the incline is *. While sliding, the acceleration of the mass is: Directed upward along the incline Directed downward along the incline Determined by the force of gravity on the mass Determined by the frictional force on the mass Determined by the normal force on the mass Determined by adding the magnitudes of the frictional and gravitational forces Determined by subtracting the magnitude of the friction force from the gravitational force Determined by adding the magnitudes of the normal and frictional forces

Answer 1

Note that the mass would not move perpendicular to the incline. So, the acceleration of the mass can only be along the incline (either up or down).

Direction of acceleration is determined by the direction of force. Note that along the incline, the component of gravitational force is down the incline. Also, since friction opposes relative motion and the mass is moving upwards, direction of friction is down the incline. So, net force along the incline is down the incline and hence direction of acceleration is downward along the incline (second option).