Olympiad Test : Force, Work And Energy - 1 - Class 5 MCQ

The change in the state of rest or uniform motion is brought about by a force. Force causes an object to either start moving, stop, or change its direction or speed (acceleration). This is described by Newton's first law of motion, which states that an object will remain in its state of rest or uniform motion unless acted upon by an external force.

Frictional force always opposes the state of motion. It acts in the opposite direction to the motion of an object, trying to resist its movement. Friction exists between two surfaces in contact and can be experienced when an object slides or tries to slide over another surface.

We sprinkle powder (usually boric powder) on the carom board to decrease friction. This reduces the resistance between the carom coins and the board, allowing the coins to move smoothly and easily when struck. Decreasing friction helps in better movement of the pieces, making the game more enjoyable.

When the load is nearer the fulcrum than the effort in a lever system, it is easier to move. This is because the lever acts as a mechanical advantage, and placing the load closer to the fulcrum allows the effort to lift the load with less force. However, it may reduce the speed of movement.

When the load is further from the fulcrum than the effort in a lever system, it becomes difficult to move. This is because the lever arm of the load becomes longer, requiring more force to lift or move the load. In such a case, the mechanical advantage decreases, making it harder to move the load.

All of these forces act on the rock as it slides across the ground:

• Gravity acts downward, pulling the rock toward the Earth.
• The normal force acts upward, balancing the force of gravity and preventing the rock from falling through the ground.
• Friction acts opposite to the direction of motion, resisting the rock's movement and gradually slowing it down.

Thus, all of these forces are acting on the rock.

• The first object has a certain mass and is accelerated by two rubber bands to 2 m/s². The force applied to the first object can be described by F = ma (Newton's second law), where m is the mass of the object and a is the acceleration.

• The second object has twice the mass of the first, and it is pulled by four rubber bands, which implies the force applied is also doubled.

Using Newton's second law for the second object:

F = m × a

Since the force is doubled (because of the four rubber bands), and the mass is also doubled, the acceleration of the second object will remain the same as the first, but it will be half because the acceleration is inversely proportional to the mass when the force is constant.

Thus, the acceleration of the second object is 4 m/s², which is double the acceleration of the first object (2 m/s²). Therefore, the correct answer is 4 m/s².

To do work on an object, you need to apply force to it, and the object must move in the direction of the force.

Work is defined as:

Work = Force × Distance

If there is no force applied, or if there is no movement in the direction of the force, no work is done. While energy is involved in the process, the key requirement for doing work is the application of force.

A simple machine is designed to make work easier by changing the direction or magnitude of a force. It can be used to lift heavy loads, increase speed, or reduce the effort required to perform tasks.

Examples of simple machines include levers, pulleys, inclined planes, screws, wedges, and wheels. These machines do not necessarily have an engine and are often used to reduce the effort needed to do work.

A book binding press is an example of a machine that uses a screw. The screw converts rotational motion into linear motion, which is used to press or fasten objects tightly together. In this case, turning the screw exerts pressure to bind the book pages or press materials together.