Answer key

Prepared by: learnloophq@gmail.com

Last edited 26 days ago by Learn LoopHQ.

Chapter: 04. Force

⁠

Section A: Multiple Choice Questions (MCQs)

b. Kicking a football

c. Change its mass

d. Muscular force

b. Frictional force

c. Rolling friction

b. To increase friction and have better grip

Section B: Fill in the Blanks

motion

shape

sufficient

non-contact

Rough

mass

Static

motion

Section C: True/False Questions

False

True

False

Section D: Short Answer Questions

Force is a push or a pull that can change or try to change an object’s state of rest or motion.

Pushing a shopping cart or pushing a button on a remote control.

If force is applied in the same direction of motion, the object begins to move faster or its speed increases.

Muscular force and frictional force.

It is difficult to write on waxed paper because its smooth surface offers very little friction between the pencil and the paper, making it hard for the graphite to transfer.

It is dangerous to drive on roads during rains because water acts as a lubricant, which significantly reduces the friction between the tires and the road, increasing the risk of skidding.

Section E: Diagram-Based Questions

Static friction is preventing the cabinet from moving.

The cabinet is not moving because the force applied by the person is not sufficient enough to overcome the static friction between the cabinet and the floor.

If another person helped, the combined force might be sufficient to overcome the static friction, causing the cabinet to start moving.

Section F: Long Answer Questions

Force can change the direction of a moving object when it is applied at an angle to the object’s current path. For instance, when a soccer player kicks an incoming football, the force from their foot changes the football’s direction of motion. Similarly, steering a bicycle by applying force to the handlebars allows you to change its direction. This redirection occurs because the applied force creates a new component of motion.

Static friction is the force that resists the start of motion when an object is at rest, like when you try to push a heavy box but it doesn’t move. Sliding friction occurs when one object slides over another, such as pushing a book across a table. Rolling friction is the resistance that occurs when an object rolls over a surface, like a wheelbarrow being pushed on a path. Rolling friction is generally much less than sliding friction, which is why wheels are so useful.

Friction is essential for human life despite its disadvantages because it enables many fundamental activities. It allows us to walk without slipping, provides the necessary grip for writing, and is crucial for vehicles to move and brake safely on roads. Without friction, simple actions like holding objects, lighting a matchstick, or even stopping a moving object would be impossible, making daily life extremely difficult and hazardous.

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