Force and Motion Class 4 SCIENCE - Orchids
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Force and Motion for Class 4 Science

  • A push or pull applied to an object can be termed a force.
  • Effects of forces are as follows:
    • Bring an object to rest into motion or change the speed of a moving object.
    • Change the shape of an object.
    • Change the direction of an object.
  • Motion can be defined as an act of change in the position of an object. Motion can be uniform or non-uniform, based on the distance covered in the specific time interval.
  • Based on the type of path of motion, it can be circular or rectilinear.
  • This concept is about types of force and motion.

Types of Forces

Question 1:

What Kind of Quantity Is Force?

Answer:

  • Force is a vector quantity
  • The quantities that have both magnitude and direction are called vector quantities.

Question 2:

Categorize the Following Into Types of Forces.

  1. Inertia
  2. Force Exerted by a Charged Body on Another Charged or Uncharged Body.
  3. The Force That Pulls Every Object Towards the Earth.
  4. The Force That Attracts a Fridge Magnet Towards the Wall of the Fridge.
  5. The Force That Helps in Skiing.
  6. The Force That Is Applied on a Hand Pump to Collect Water.

Answer:

  1. Not a force.
  2. Electrostatic force.
  3. Gravitational force.
  4. Magnetic force.
  5. Frictional force.
  6. Mechanical force.

Question 3:

What Is Inertia?

Answer:

  • Inertia is the property of an object by virtue of which it either remains in a static state or uniform motion.
  • Uniform motion can be defined as the motion of an object where it covers equal distances in equal time intervals.

Question 4:

What for Sir Isaac Newton is Famous?

Answer:

  • Sir Isaac Newton was a famous scientist who worked on force and gravity.
  • He invented calculus and the theory of universal gravity and coined three laws of motion.
  • He also invented the reflecting telescope that can form an image with the help of reflecting mirrors.

Question 5:

What Is Centrifugal Force? Give Examples.

Answer:

  • The centrifugal force is an apparent force felt on an object when moving in a circular path.
  • Example- Sensation of force felt while we sit in a merry-go-round moving in a circular direction is due to the centrifugal force.
Centrifugal Force

Question 6:

Arrange the Following Animals in Ascending Order According to Their Inertia.

Animals

Why is the magnitude of inertia different among all these animals?

Answer:

  • Inertia exerted by a body or object is directly proportional to its mass.
  • The more the mass, the more inertia is exerted by it.
  • Hence, the order of the animals in ascending sequence would be Ant< Caterpillar< Lizard< Cat< Bear< Elephant.

Question 7:

Why Are Bogies of Trains Provided With Buffers?

Answer:

  • Bogies of trains are provided with buffers because those increase the impact of jerking between two bogies, preventing the sudden jerking of the passengers sitting inside.
Buffer

Question 8:

Why Do Two Thermocol Balls Always Move Away From Each Other?

Answer:

  • Two thermocol balls move away from each other because electrostatic force acts on those balls.
  • As both balls have similar charges in their bodies, they repel each other.

Question 9:

What Are the Poles of a Magnet?

Answer:

  • The ends of the magnet are termed poles.
  • A magnet has two poles, a north pole and a south pole.
  • The same poles of a magnet repel each other.
  • The opposite poles of a magnet attract each other.
Poles of a Magnet

Force and Pressure

Question 1:

See the Picture and Answer the Following Questions-

  1. Which Point Has the Highest Sideways Pressure?
  2. Which Point Has the Lowest Sideways Pressure?
  3. What Will Happen to the Lateral Pressure of C if the Water Level Is Reduced?
  4. How Can the Magnitude of Pressure Be Increased at the Bottom of a Container Half-Filled With a Liquid?
variation of pressure with height

Answer:

  1. Point C has the highest sideways pressure.
  2. Point A has the lowest lateral pressure.
  3. The lateral pressure will reduce at point C if the water level is reduced.
  4. If a container is half-filled with a liquid, the pressure at the bottom can be increased by pouring more liquid into that container.

The height of liquid inside a container is directly proportional to the pressure at the bottom of the container.

Question 2:

A Force of 400 N Is Applied to an Area of 4 m2. Calculate the Pressure Applied to the Site.

Answer:

  • The pressure applied to the area will be:
    Pressure= Force/ Area that means 400/4 = 100 Pascal.

Question 3:

What Is the Formula of Pressure in the S.I. Unit?

Answer:

  • The formula of pressure in the S.I. unit is- Pressure = Force/ Unit Area = N/ m2 i.e. Newton per metre square.

Question 4:

Identify the types of motions in the following images-

circular motion
rectilinear motion
periodic motion

Answer:

  1. The motion of a satellite- Circular motion.
  2. The motion of a moving car- rectilinear motion.
  3. The motion of a swing- Periodic motion.

Question 5:

What is revolution of the Earth?

Answer:

  • The rotation of Earth around the sun in a circular orbit is called revolution.
  • One revolution takes 365.26 days to complete.
revolution of the Earth

Types of Levers

Question 1:

Give three examples of levers that we use in our daily life and mention their class.

Answer:

Three levers that we use in our daily life are-

  • Plier: Class I lever.
  • Scissors: Class I lever.
  • Wheelbarrow: Class II lever.
Types of Levers

Question 2:

What is the importance of a fulcrum in a lever?

Answer:

  • The fulcrum is the pivot point of the lever.
  • The fulcrum is situated between the load and effort point, the distance between load and fulcrum is called the load arm and the distance between effort, and the fulcrum is called the effort arm.
  • If the fulcrum is closer to the load, the lever has a bigger effort arm which takes minimal effort to work.
  • If the fulcrum is closer to the effort, the lever has a bigger load arm that takes more effort.
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