G11 Physics Term 3 Exam Review

Which of the following quantities is a vector?

• Speed

• Distance

• Velocity

• Mass

Answer explanation

A vector is a quantity that has both magnitude (size) and direction. Let’s analyze each option:

Speed – Scalar ❌

Speed is the rate of motion but has no direction.

Example: A car moving at 60 km/h is speed, but 60 km/h north is velocity.

Distance – Scalar ❌

Distance measures the total length traveled, but it does not consider direction.

Example: Running 5 km is distance, but "5 km east" would involve displacement (a vector).

Velocity – Vector ✅

Velocity is speed with a direction.

Example: A car moving at 60 km/h north has both magnitude (speed) and direction, making it a vector.

Mass – Scalar ❌

Mass is only a measure of matter in an object and has no direction.

Example: A 10 kg object has mass but no directional component.

If a car travels 30 meters in 2 seconds, what is its average speed?

• 10 m/s

• 15 m/s

• 20 m/s

• 30 m/s

Answer explanation

The formula for average speed is:

Speed = Distance ÷ Time

where:

Distance = 30 meters

Time = 2 seconds

Step 1: Calculate the Speed

Speed =30 m ÷ 2s

Speed = 15 m/s

The acceleration due to gravity on Earth is:

• 8.9 m/s2

• 9.8 m/s2

• 10.8 m/s2

• 12.2 m/s2

Answer explanation

The acceleration due to gravity on Earth, denoted as g, is 9.8 m/s².

This means that an object in free fall will increase its velocity by 9.8 m/s every second if air resistance is ignored.

Which of the following is an example of Newton’s First Law of Motion?

• A rocket accelerating in space.

• A car skidding to a stop when the brakes are applied.

• A book remaining at rest on a table.

• A swimmer pushing against water and moving forward.

Answer explanation

Newton’s First Law of Motion (also called the Law of Inertia) states:
An object at rest stays at rest, and an object in motion stays in motion at a constant velocity unless acted upon by an external force.

The book remains at rest because no external force is acting on it to change its state of motion, which is the definition of Newton's First Law.

An object in free fall experiences:

• Constant velocity

• Increasing acceleration

• Constant acceleration

• Zero acceleration

Answer explanation

An object in free fall is only affected by gravity, meaning it accelerates at a constant rate of 9.8 m/s² on Earth.

This means that every second, the velocity increases by 9.8 m/s, but the acceleration remains constant.

Which unit is used to measure force?

• Joule

• Newton

• Watt

• Pascal

Answer explanation

Force is measured in Newtons (N), named after Sir Isaac Newton.

The unit is derived from Newton’s Second Law of Motion: F=ma

A ball is thrown straight up into the air. At the highest point, its velocity is:

• Maximum

• Zero

• Equal to its acceleration

• Same as its initial velocity

Answer explanation

When a ball is thrown straight up, it slows down as it moves against gravity.

At the highest point, the ball momentarily stops before falling back down.

Velocity at this moment is zero because the ball is neither moving up nor down at that exact instant.

However, acceleration due to gravity (9.8 m/s² downward) still acts on it, causing it to start falling immediately after.

Which of the following describes Newton’s Third Law of Motion?

• Acceleration depends on force and mass.

• Objects in motion stay in motion unless acted upon by an external force.

• Every action has an equal and opposite reaction.

• The total momentum in a system remains constant.

Answer explanation

Newton’s Third Law of Motion states:
"For every action, there is an equal and opposite reaction."

This means that whenever an object exerts a force on another object, the second object exerts an equal force in the opposite direction.

Examples:

When you push against a wall, the wall pushes back with equal force.

When a rocket pushes gases downward, the gases push the rocket upward.

Momentum is the product of:

• Mass and acceleration

• Mass and velocity

• Force and distance

• Force and time

Answer explanation

Momentum (p) is a measure of an object's motion and is calculated using the formula:

p=mv

Where:

p = momentum (kg·m/s)

m = mass (kg)

v = velocity (m/s)

This means momentum depends on both mass and velocity—a heavier or faster-moving object has more momentum.

If two forces act on an object in opposite directions and are equal in magnitude,

the object will:

• Accelerate in the direction of the larger force

• Move at constant velocity

• Remain at rest or move at constant velocity

• Accelerate in the opposite direction

Answer explanation

When two forces act in opposite directions with equal magnitude, they cancel each other out, resulting in a net force of zero.

According to Newton’s First Law of Motion (Law of Inertia):

If an object is at rest, it will stay at rest.

If an object is already moving, it will continue moving at a constant velocity (no acceleration).