DYNAMIC

What is the primary challenge in applying Newton’s Second Law to particle motion?

• Calculating velocity

• Measuring the particle's weight

• Estimating time of motion

• Identifying all forces acting on the particle

Answer explanation

Accurately identifying all the forces acting on a particle is crucial for solving problems using Newton's Second Law. Missing or misrepresenting forces (e.g., friction or normal force) can lead to incorrect calculations and understanding of the motion.

A block slides down an inclined plane. Which forces should be included in the free-body diagram?

• Friction, normal force, and weight

• Friction, tension, and centripetal force

• Tension, weight, and friction

• Normal force and centripetal force

Answer explanation

For a block on an inclined plane, the forces acting on it are:

• Weight (gravity): Acts vertically downward.

• Normal force: Acts perpendicular to the surface of the plane.

• Friction: Acts parallel to the surface, opposing motion.
  Tension and centripetal forces do not apply in this scenario.

If a particle experiences a net force of 20 N and a mass of 4 kg, what is its acceleration?

• 2 m/s²

• 4 m/s²

• 5 m/s²

• 10 m/s²

Answer explanation

Newton’s Second Law states F=ma

Rearranging to solve for acceleration:
a=Fm=20 N/4 kg=5 m/s2

What is the normal force?

• The force that is perpendicular to the surface between two objects

• The force that causes objects to stick together

• The force that pushes objects together

• None of the above

Answer explanation

The normal force is a contact force exerted by a surface on an object in response to the object's weight. It acts perpendicular (or normal) to the surface.

Amirul is trying to push a heavy box across a surface. How does friction affect the movement of the box?

• It increases the speed of objects

• It decreases the speed of objects

• It has no effect on the speed of objects

• It can either increase or decrease the speed depending on the surfaces

Answer explanation

The amount of friction depends on the nature of the surfaces involved. For example, rough surfaces like sandpaper generate more friction than smooth surfaces like ice. Friction can either slow down a moving object (kinetic friction) or provide the grip needed to start moving (static friction).

Amira is pushing her skateboard down the street. What is the effect of her force on the skateboard?

• It changes the object's speed or direction

• It increases the object's mass

• It determines the object's speed

• It has no effect on the object

Answer explanation

When Amira applies a force to her skateboard, it results in a change in the skateboard's speed or direction. According to Newton's second law of motion, the force applied to an object causes an acceleration, which changes the velocity of the object. This means the skateboard will either speed up, slow down, or change direction based on the force applied by Amira.

What is the unit of measurement of force?

• meter (m)

• second (s)

• Newton (N)

• Kilogram (kg)

Answer explanation

• Newton (N): This is a unit of force.

• meter (m): This is a unit of length or distance.

• second (s): This is a unit of time.

• Kilogram (kg): This is a unit of mass.