7 A block of mass 30 kg is dragged across a rough horizontal surface by a rope that is at an angle of \(20 ^ { \circ }\) to the horizontal. The coefficient of friction between the block and the surface is 0.4 .
- The tension in the rope is 150 newtons.
- Draw a diagram to show the forces acting on the block as it moves.
- Show that the magnitude of the normal reaction force on the block is 243 newtons, correct to three significant figures.
- Find the magnitude of the friction force acting on the block.
- Find the acceleration of the block.
- When the block is moving, the tension is reduced so that the block moves at a constant speed, with the angle between the rope and the horizontal unchanged. Find the tension in the rope when the block is moving at this constant speed.
- If the block were made to move at a greater constant speed, again with the angle between the rope and the horizontal unchanged, how would the tension in this case compare to the tension found in part (b)?