Four solid spheres are made to move on a rough horizontal surface. Sphere P is given a spin and released. Sphere Q is given a forward linear velocity. Spheres R and S are given linear and rotational motions as shown in the figure. Directions of the friction force on spheres P, Q, R and S are respectively.
ln sphere P, the point of contact has tendency to move towards left w.r.t. surface and hence, friction acts on it towards right.
In spheres Q and R, the point of contact has tendency to move towards right w.r.t. surface and hence, friction acts on both of them towards left.
ln sphere S, the point of contact has tendency to move towards left due to rotation and towards right due to translator motion. It has not been specified in question whether v is less than or greater than R. Hence, friction on it may act towards left or right.
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