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physics Advanced Subsidiary (AS) Level Physics.

Solved problems for the chapter:

Frictional Force

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Newton's First Law of Motion for KS4

1. Newton's first law

2. Equilibrium of forces

2.1. Equilibrium of two forces

2.2. Equilibrium of several forces

2.2.1. Parallelogram rule

2.2.2. Polygon forces

3. Forum

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Introduction to Force

1. What is force?

2. How do we know that a force is acting on a body?

2.1. Effects of forces

3. Name, symbol and unit of force

4. Properties of force

5. Drawing forces

6. Contact force or field force

7. Surface and volume distributed forces

7.1. Area-distributed or surface forces

7.2. Volume-distributed or body forces

8. Measuring forces

9. Forum

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Friction and bonding force

1. Static frictional force

2. Dynamic frictional force

3. Forum

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Forces on an Inclined Plane

1. Components of the weight of a body on an inclined plane

1.1. Determination of the components of the weight of a body on an inclined plane using similar triangles

1.2. Determination of the components of the weight of a body on an inclined plane using angular functions

2. Forces and motion of a body on an inclined plane

3. Forum

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Detailed solution steps are available at:

https://en.openprof.com/wb/chapter:frictional_force/4017/

Example 1.

Joe pulls a sled at an angle to the horizontal surface. The frictional force between the sled and the snow is 42 N. With what force does Joe pull the sled to move uniformly?

Example 2.

A body with mass m is dragged at a constant speed over a rough surface. The force is measured with a force metre (spring balance). The force metre shows a force of 0.6 N. What is the value of the frictional force? If we slightly increase the speed, will the force metre show the same force?

A 200 g box is dragged with a spring balance on a horizontal rough surface so that it moves uniformly. The force shown by the spring balance is 0.3 N.

What is the frictional force?
If another box of the same mass is placed on the previous box, what is the force required for uniform motion now, and what is the friction force?

A rectangular box of lengths of edges:

is dragged on a horizontal rough surface on a side with edges a, b. The mass of the box is 10 kg. If the box is pulled at a constant speed, a force of 20 N is applied. What is the frictional force? What is the frictional force if the box is pulled on a side with edges a, c and b, c.

On the table is a log weighing 2 kg. The log is attached to a string passed over an attached pulley to an unknown weight, as shown in the figure. What is the mass of the unknown weight so that the log will move uniformly? The frictional force between the log and the base is 4 N.

A body slides uniformly down a slope with frictional force of 4 N. What is the dynamic component of the weight? How much force do we need to pull it with to move it uniformly up the slope?

A box of mass 4 kg slides uniformly down a slope at an angle of inclination . What is the frictional force between the box and the slope?

Two blocks of masses 1.5 kg and 1 kg are connected by a string as shown. A rope is attached to the right block and pulled so that both blocks slide at a constant speed v on a flat, rough surface. The frictional force of the right block is 3 N and that of the left 2 N. What is the force in the pulling rope and what is the force in the rope connecting the two blocks?

A box at a uniform speed glides down a slope at an inclination of . The frictional force between the box and the slope is 6 N. What is the mass of the box?

10.

A crate weighing lies on the ground. A force of is applied to move it.

Draw all the forces acting on the body.
What is the coefficient of friction?
What is the force exerted on the ground by the crate before it begins to move?

11.

A block with a mass of lies on a flat surface. It is acted upon by a force of at an angle of with respect to the horizontal. At a slightly higher force, the body begins to move, what is the coefficient of static friction between the body and the surface?

12.

A wooden log with a mass of is pressed against the wall. How much force do we have to exert on the log to keep it from slipping if the coefficient of static friction between the log and the wall is ?

13.

On the table lies a body with a mass of . The body is connected by a pulley to another body with a mass of . What must be the coefficient of static friction between the table and the first body so that the body does not slip?

14.

On a table lies a body with mass . The body is connected with a string via a pulley to another body of mass . The coefficient of friction between the first body and the table is . With how much force do we have to pull the first body to slide uniformly and the second to lift uniformly?

15.

A log lies in a gutter. The gutter is V-shaped and the angle between the sides of the gutter is . With what force do we have to pull the log in the direction of its axis to make it move uniformly? The coefficient of friction between the log and the gutter is .

16.

Two bodies with masses and are connected with a cord on a horizontal base as shown below.

Mass on string

The coefficient of friction of the first body is and the second is .

What force is needed to move the two bodies uniformly?
What force is needed to pull uniformly with the cord between the bodies?

17.

What is the initial velocity of a body sliding on a rough horizontal surface if it stops at a distance of ? The coefficient of friction between the body and the surface is .

18.

Three bodies of equal mass are connected by a rope and placed on a slope as shown in the figure. The slope angle is . What should be the coefficient of friction between the bodies and the slope so that they do not slip?

19.

A body lies on an inclined plane. The slope of the inclined plane is slowly increased until the body slips. This happens at angle . What is the coefficient of static friction between the body and the plane?

20.

A sled slides uniformly down an inclined plane with a 15 percent slope. What is the coefficient of kinetic friction between the sled and the plane?

21.

A car of mass has a horizontal driving force of acting on it. It has a forward horizontal acceleration of .

What is the resistive force acting horizontally?

22.

A box in air slides with increasing speed down a rough slope from point P to point Q.

The slope surface exerts a constant frictional force on the box. As the box moves from P to Q, there are changes to the magnitudes of its acceleration and the total resistive force acting on it. Which row describes the changes?

	magnitude of acceleration	magnitude of total resistive force
A	increases	decreases
B	decreases	decreases
C	increases	increases
D	decreases	increases

23.

A child on a sledge slides down a hill with acceleration . The hill makes an angle with the horizontal.

The total mass of the child and the sledge is . The acceleration of free fall is . What is the frictional force ?

24.

An ice-hockey puck of mass moves with an initial speed of along the surface of an ice rink. The puck slides a distance of in a straight line before stopping. What is the average frictional force acting on the puck?

25.

A car of mass travels at constant speed up a slope at an angle to the horizontal, as shown in the diagram. Air resistance and friction provide a resistive force . The acceleration of free fall is .

What is the force needed to propel the car at this constant speed?