Get premium membership and access questions with answers, video lessons as well as revision papers.
1.Gravitational force
It is the force that attracts all objects towards the centre of the earth. It is unique in every planet. The earth’s
gravitational force is that force of attraction between the earth and the body. The pull of gravity on a body
towards the centre of the earth is called its weight. Weight varies from place to place although its mass remains
constant.
The weight of a body is the product of its mass and the gravitational force acting on the body
i.e. weight =mass *gravitational force.
2: Tension
When a string is stretched or compressed at both of its ends, it experiences a force called tension. A stretched or
compressed material will tend to regain its original shape when the stretching or compressing force is
withdrawn. Materials that do not break after stretching or compression is said to be elastic.
Upthrust
When an object is immersed in a fluid (liquid/gas), there is always an opposite upward force acting on it. This is
called upthrust force.
NB. There is no upthrust force in a vacuum.
Upthrust force = Weight of object when in air -- Weight of the object when immersed in fluid (Apparent weight of the object)
3: Friction force
This is the force that tends to oppose the motion of one object over another when they are in contact. Friction
force is useful in many ways for instance during walking, writing, applying brakes, lighting a match stick, etc.
Friction in fluids is called viscous drag or simply viscosity.
5: Magnetic force
A magnet can either attract or repel a magnetic material. This force of attraction or repulsion is called magnetic
force. Materials that are not affected by a magnet are said to be non-magnetic materials.
6: Electrostatic force
This is the force of attraction or repulsion between static charges. Like charges repel while unlike charges attract.
Electrostatic force is evident in the following cases:
A plastic pen or ruler rubbed on dry air picks up small pieces of paper placed on a table.
Such a pen can attract a stream of water from a water tap.
A glass window wiped using a dry piece of cloth on a dry day immediately attracts dust particles.
Brushed shoes attract dust particles.
When combing a dry hair, a cracking sound is produced.
All these are as a result of attraction between the formed charges and the opposite charges.
7: Centripetal force
This is the force that constraints a body to maintain a circular path as it move. It is usually directed towards the
centre of the circle.
8: Action and reaction
Action and reaction are equal and opposite forces. When a block of wood rests on a table its weight is exerted on
the table. This is action force. The table on the other hand exerts an equal upward force on the block of wood.
This is reaction force and it prevents the block from sinking down below the table.
9: Cohesive and adhesive force
Cohesive force is the force of attraction between molecules of the same kind e.g. force between water molecules.
Adhesive force is the force of attraction between molecules of different kinds e.g. force between water molecule
and the surface of glass.
10: Surface tension
The cohesive force between the molecules of a liquid gives it some strength. The surface can thus resist
stretching. Surface tension is the force that makes the surface of the liquid to behave like a fully stretched elastic
skin.
Surface tension allows light insects to rest over water without sinking. a steel razor blade or needle floats on
water if placed carefully but sinks when soap solution or kerosene is placed around it. Also if one end of the
needle is pressed into the water, it breaks the surface tension and the needle sinks.
Molecular explanation of surface tension
Moraa orina answered the question on April 6, 2018 at 14:53
- State thr effects of force on a body
(Solved)
State the effects of force on a body
Date posted: April 6, 2018. Answers (1)
- 1800cm3 of fresh water of density 1000kgm-3 is mixed with 2200cm3 of sea water of density 1025kgm-3.
Calculate the density of the mixture in gcm-3.(Solved)
1800cm3 of fresh water of density 1000kgm-3 is mixed with 2200cm3 of sea water of density 1025kgm-3.
Calculate the density of the mixture in gcm-3.
Date posted: April 6, 2018. Answers (1)
- The mass a 50cm3 density bottle is 10.0g when empty and 60.0g when filled with copper turnings upto a certain level. Some water is...(Solved)
The mass a 50cm3 density bottle is 10.0g when empty and 60.0g when filled with copper turnings upto a
certain level. Some water is added into the bottle until it is full. The mass of the bottle and its contents is found to be 90.0g. Determine the density of the copper turnings.
Date posted: April 6, 2018. Answers (1)
- An object of mass 50.1g has a density of 16.7gcm-3. What is the volume of the object?(Solved)
An object of mass 50.1g has a density of 16.7gcm-3. What is the volume of the object?
Date posted: April 6, 2018. Answers (1)
- The number of molecules in 18 cm cubic of a liquid is 6 multiplied by 10 powered 23. assuming the diameter of the molecule is equivalent to...(Solved)
The number of molecules in 18 cm cubic of a liquid is 6 multiplied by 10 powered 23. Assuming the diameter of the molecule is equivalent to the side of a cube having the same length as the molecule. Determine the diameter of the molecule.
Date posted: April 6, 2018. Answers (1)
- Describe how to find the volume of irregularly shaped object using a eureka can(Solved)
Describe how to find the volume of irregularly shaped object using a eureka can
Date posted: April 5, 2018. Answers (1)
- Describe how to measure the volume of irregularly shaped object using a measuring cylinder(Solved)
Describe how to measure the volume of irregularly shaped object using a measuring cylinder
Date posted: April 5, 2018. Answers (1)
- State the disadntages of alkaline accumulators over lead-acid accumulators(Solved)
State the disadntages of alkaline accumulators over lead-acid accumulators
Date posted: April 5, 2018. Answers (1)
- A battery is rated at 30 Ah. For how long will it work if it steadily supplies a current of 3 A?(Solved)
A battery is rated at 30 Ah. For how long will it work if it steadily supplies a current of 3 A?
Date posted: April 5, 2018. Answers (1)
- The current in a single loop is 3.0 A. How long would it take for a charge of 3600
coulombs to flow?(Solved)
The current in a single loop is 3.0 A. How long would it take for a charge of 3600
coulombs to flow?
Date posted: April 5, 2018. Answers (1)
- The length of a pinhole camera is 25.0 cm. An object 2.0 cm is placed 10.0 m from the
pinhole. Calculate the height of the...(Solved)
The length of a pinhole camera is 25.0 cm. An object 2.0 cm is placed 10.0 m from the
pinhole. Calculate the height of the image produced and its magnification
Date posted: April 5, 2018. Answers (1)
- Calculate the height of a building 300 m away from a pinhole camera which produces
an image 2.5 cm high if the distance between the...(Solved)
Calculate the height of a building 300 m away from a pinhole camera which produces
an image 2.5 cm high if the distance between the pinhole and the screen is 5.0 cm.
Date posted: April 5, 2018. Answers (1)
- List four applications of radiation(Solved)
List four applications of radiation.
Date posted: April 5, 2018. Answers (1)
- State the applications of conductors(Solved)
State the applications of conductors
Date posted: April 5, 2018. Answers (1)
- Starting a car with 12 volts battery is better than 12 dry cells in series.Explain(Solved)
Starting a car with 12 volts battery is better than 12 dry cells in series.Explain
Date posted: April 5, 2018. Answers (1)
- The master cylinder piston in a car braking system has a diameter of 2.0 cm. The
effective area of the brake pads on each of...(Solved)
The master cylinder piston in a car braking system has a diameter of 2.0 cm. The
effective area of the brake pads on each of the four wheels is 30 cm2
. The driver
exerts a force of 500 n on the brake pedal. Calculate
a) The pressure in the master cylinder
b) The total braking force in the car.
Date posted: April 4, 2018. Answers (1)
- The area of the smaller piston of a hydraulic press is 0.01 m2 and that of the bigger piston is 0.5 m2. If the force...(Solved)
The area of the smaller piston of a hydraulic press is 0.01 m2
and that of the bigger
piston is 0.5 m. If the force applied to the smaller piston is 2 N, what force is
transmitted to the larger piston?
Date posted: April 4, 2018. Answers (1)
- Explain how a hydraulic press works(Solved)
Explain how a hydraulic press works
Date posted: April 4, 2018. Answers (1)
- Describe how a hydraulic brake system works(Solved)
Describe how a hydraulic brake system works
Date posted: April 4, 2018. Answers (1)
- Explain the applications of pressure in gases and liquids(Solved)
Explain the applications of pressure in gases and liquids
Date posted: April 4, 2018. Answers (1)