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physics Physics For High Schools (KS4)
 
Solved problems for the chapter:
 

Friction

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Detailed solution steps are available at:
 
https://en.openprof.com/wb/chapter:friction/5059/


Example 1.

Determine whether the statements are correct:

  • Frictional force acts in the direction of the body's motion.

  • Friction is greater if the body mass is greater and if the contact surface between the body and the ground is rougher.

  • Friction is greater at higher body speeds.

  • Friction is independent of the size of the contact area between the body and the ground.

  • Friction is low during skating because the ice is smooth.

  • When a boatman paddles on water, the motion is hindered by friction between the boat and the water.

    
Example 2.

Are the following statements correct?

  • There is no physical difference between friction and resistance.

  • Resistance occurs during the motion of a body in air or water.

  • The resistance is independent of speed.

  • Resistance depends on body shape.

  • The resistance does not depend on the size of the body surface in the direction of motion.

    
3.

List three items designed to create as much and as little friction as possible.

    
4.

Three trains run at the same speed for a moment. Compare the magnitudes of air resistance for all thr three trains.


    
5.

On the river, three differently shaped pillars in the middle of the river support three bridges. In the picture, the columns are drawn in a horizontal section. Examine which pillar will offer the smallest and which the largest resistance to the river? We assume that the river is equally deep in all three cases and flows equally fast.


    
6.

A cyclist is travelling in a straight line along a horizontal road at a constant speed. A constant driving force F acts on the cyclist in the forward direction shown.




Which statement about the magnitude of the frictional force acting on the cyclist is correct?


  • The magnitude is equal to F.

  • The magnitude is smaller than F, but greater than zero.

  • The magnitude is greater than F.

  • The magnitude is zero.

    
7.

A train is travelling horizontally in a straight line. A book is on a table in the train. The diagram shows all the forces acting on the book.




How is the train moving?


  • accelerating to the left of the diagram

  • accelerating to the right of the diagram

  • moving at uniform speed to the left of the diagram

  • moving at uniform speed to the right of the diagram

    
8.

A box of mass is pulled across a horizontal floor by a force of . The frictional force acting on the box is . What is the acceleration of the box?






    

9.

Which force produces heating during contact with a moving object?


  • weight

  • friction

  • electrostatic force

  • magnetic force

    
10.

Which are examples of friction?


  • tension in a spring

  • air resistance

  • weight


  • 1 only

  • 1 and 3

  • 2 only

  • 2 and 3

    
11.

A sledge is pulled in a straight line by dogs, as shown.




The dogs produce a total horizontal driving force of . The frictional force between the sledge and the surface is and the air resistance on the sledge is . What is the resultant force acting on the sledge?