Science Class 8 CBQ of Exploring Forces (Remarkable Push)

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Science Class 8 CBQ of Exploring Forces

Case 1: Sonali and Ragini’s Cycling Adventure

Sonali and Ragini set off on a cycling trip on a windy day. As they rode, Ragini felt the wind pushing hard against her, and Sonali noted they had to push their pedals harder to move against it. Later, they cycled up a long path to a hilltop where they noticed some parts of the road were rough and harder to pedal, while other parts were smooth. On their return trip, as they came down the slope, their bicycles moved at great speed even without pedalling.

  1. Which type of force was Ragini experiencing when the wind “pushed” against her?
  1. Magnetic force
  2. Electrostatic force
  3. Contact force
  4. Non-contact force
  1. Why was it harder for the girls to pedal on the “rough” parts of the road compared to the “smooth” parts?
  1. Friction is greater on rough surfaces.
  2. There was more gravity on rough roads.
  3. Rough roads have no irregularities.
  4. Muscular force only works on smooth surfaces.
  1. When the bicycles moved down the slope at high speed without pedalling, which force was primarily responsible for pulling them downhill?
  1. Frictional force
  2. Gravitational force
  3. Electrostatic force
  4. Magnetic force

Science Class 8 CBQ of Exploring Forces

  1. To change the direction of their bicycles to avoid a herd of sheep, the girls had to:
  1. Apply a force to the handles.
  2. Increase their mass.
  3. Stop the interaction between the tires and the road.
  4. Wait for a non-contact force to act.
  1. Sonali’s statement about “pushing pedals harder” refers to the application of:
  1. Magnetic force
  2. Muscular force
  3. Electrostatic force
  4. Gravitational force

Science Class 8 CBQ of Exploring Forces

Case 2: The Moving Cardboard Box

In an activity, students are asked to take a large cardboard box and move it in different ways: pushing it, pulling it, or lifting and carrying it. The text explains that in all these instances, a force is being applied to the object. In science, force is described as a push or pull on an object caused by its interaction with another object.

  1. According to the text, what is the scientific definition of force?
  1. Only a push applied to an object
  2. Only a pull applied to an object
  3. A push or pull resulting from an interaction
  4. The weight of a moving object
  1. When a student lifts the box up, which two objects are interacting?
  1. The box and the floor
  2. The student’s hand and the box
  3. The box and the air
  4. The floor and the student’s feet

Science Class 8 CBQ of Exploring Forces

  1. What is the SI unit of the force applied to the box?
  1. Gram (g)
  2. Newton (N)
  3. Kilogram (kg)
  4. Meter (m)
  1. If the box is at rest on the floor, does it mean no forces are acting on it?
  1. Yes, forces only act on moving objects.
  2. No, it means the forces acting on it are balancing one another.
  3. Yes, interaction only happens during movement.
  4. No, only magnetic forces can act on stationary objects.
  1. If a student pushes the box and it starts to move, the force has caused:
  1. A change in the box’s shape
  2. An object to move from rest
  3. the box to lose mass
  4. A non-contact interaction

Science Class 8 CBQ of Exploring Forces

Case 3: Exploring Non-Contact Forces

A student performs three experiments. First, they bring two ring magnets together and find they can repel or attract without touching. Second, they rub a plastic scale with polythene and find it attracts small pieces of paper. Third, they observe a ball thrown upwards eventually falling back to the Earth. These are all identified as non-contact forces because they act from a distance.

  1. Which of the following is a similarity between magnetic and electrostatic forces?
  1. They both only attract objects.
  2. They can both be either attractive or repulsive.
  3. They both require physical contact.
  4. They only act on wooden objects.
  1. Why does the rubbed plastic scale attract paper pieces?
  1. It becomes magnetized.
  2. It acquires static electrical charges.
  3. It increases in mass.
  4. The paper pieces are made of metal.
  1. Gravitational force is different from magnetic force because:
  1. It is always a repulsive force.
  2. It always pulls objects toward one another.
  3. It is a contact force.
  4. It does not act on non-metals.

Science Class 8 CBQ of Exploring Forces

  1. When two similarly charged balloons are brought together, they will:
  1. Attract each other
  2. Repel each other
  3. Change their shape
  4. Lose their charge immediately
  1. Non-contact forces are defined as forces that:
  1. Only work in a vacuum
  2. Can be experienced even if objects are not in contact
  3. Require a rope or stick to act
  4. Only act on living beings

Science Class 8 CBQ of Exploring Forces

Case 4: The Mystery of Friction

A ball rolling on flat ground eventually stops on its own. In the same way, a bicycle loses speed when we stop pedaling. This is due to the force of friction, which arises because of irregularities in the two surfaces in contact. The direction of friction is always opposite to the object’s movement. Engineers design high-speed trains and aeroplanes with specific shapes to reduce the friction caused by air or water.

  1. In which direction does the force of friction act on a sliding notebook?
  1. In the direction of its motion
  2. In a direction opposite to its motion
  3. Vertically upwards
  4. Vertically downwards
  1. Why do surfaces that appear smooth still experience friction?
  1. They have no irregularities.
  2. They contain many tiny surface irregularities.
  3. Because of gravitational pull.
  4. Because they are in a vacuum.

Science Class 8 CBQ of Exploring Forces

  1. What happens to the speed of a ball rolling on the ground due to friction?
  1. Its speed increases.
  2. Its speed remains constant.
  3. Its speed gradually decreases until it stops.
  4. Its direction changes randomly.

Science Class 8 CBQ of Exploring Forces

  1. Why are ships and aeroplanes designed with “specific shapes”?
  1. To make them look beautiful.
  2. To increase the force of friction.
  3. To reduce the force of friction from air or water.
  4. To increase their weight.
  1. Friction is classified as a:
  1. Non-contact force
  2. Contact force
  3. Magnetic force
  4. Electrostatic force

Science Class 8 CBQ of Exploring Forces

Case 5: Weight, Mass, and Buoyancy

Mass refers to the quantity of matter in an object and stays constant regardless of location. Weight is the gravitational force with which the Earth pulls an object and can vary from place to place. In another experiment, pushing a plastic bottle into a bucket of water reveals an upward force called upthrust or buoyant force. If the gravitational force is more than the buoyant force, the object sinks; otherwise, it floats.

  1. If an object with a mass of 1 kg is taken from Earth to the Moon, what happens to its mass?
  1. It becomes 1/6th of 1 kg.
  2. It becomes 6 kg.
  3. It remains 1 kg.
  4. It becomes zero.
  1. Which instrument is used to measure the weight of an object?
  1. Thermometer
  2. Beam balance
  3. Spring balance
  4. Measuring tape
  1. An object floats on water when:
  1. The gravitational force is more than the buoyant force.
  2. the gravitational force and buoyant force are equal.
  3. There is no gravitational force.
  4. The object is made of magnetic material.

Science Class 8 CBQ of Exploring Forces

  1. What unit is used to measure weight in the SI system?
  1. Kilogram (kg)
  2. Gram (g)
  3. Newton (N)
  4. Liter (L)
  1. Why does a mug seem lighter when submerged in a bucket of water?
  1. It loses mass inside the water.
  2. Water applies an upward buoyant force on it.
  3. The Earth stops pulling it.
  4. it becomes a charged object.

Science Class 8 CBQ of Exploring Forces

Answer Key

Case 1: Sonali and Ragini’s Cycling Adventure

  1. (c) Contact force.
  2. (a) Friction is greater on rough surfaces.
  3. (b) Gravitational force.
  4. (a) Apply a force to the handles.
  5. (b) Muscular force.

Case 2: The Moving Cardboard Box

  1. (c) A push or pull resulting from an interaction.
  2. (b) The student’s hand and the box.
  3. (b) Newton (N).
  4. (b) No, it means the forces acting on it are balancing one another.
  5. (b) An object to move from rest.

Case 3: Exploring Non-Contact Forces

  1. (b) They can both be either attractive or repulsive.
  2. (b) It acquires static electrical charges.
  3. (b) It is always an attractive force.
  4. (b) Repel each other.
  5. (b) Can be experienced even if objects are not in contact.

Case 4: The Mystery of Friction

  1. (b) In a direction opposite to its motion.
  2. (b) They contain many tiny surface irregularities.
  3. (c) Its speed gradually decreases until it stops.
  4. (c) To reduce the force of friction from air or water.
  5. (b) Contact force.

Case 5: Weight, Mass, and Buoyancy

  1. (c) It remains 1 kg.
  2. (c) Spring balance.
  3. (b) The gravitational force and buoyant force are equal.
  4. (c) Newton (N).
  5. (b) Water applies an upward buoyant force on it.

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