Physics - Term 4 - Week 2

Kinematics is the branch of physics that describes the motion of objects. It focuses on the concepts of displacement, velocity, and acceleration. Displacement is the change in position of an object and is a vector quantity, meaning it has both magnitude and direction. Velocity, also a vector, is the rate of change of displacement over time. Acceleration is the rate of change of velocity and can be positive (speeding up) or negative (slowing down). Understanding these concepts is crucial for analyzing motion.

A car travels 150 meters to the east in 5 seconds. To find the velocity, we use the formula: velocity = displacement / time. Here, the displacement is 150 meters and the time is 5 seconds. Thus, the velocity is 150 m / 5 s = 30 m/s to the east. This example illustrates how to calculate velocity from displacement and time.

Consider a bicycle that accelerates from rest to a speed of 20 m/s in 4 seconds. To find the acceleration, we use the formula: acceleration = (final velocity - initial velocity) / time. The initial velocity is 0 m/s, and the final velocity is 20 m/s. Therefore, acceleration = (20 m/s - 0 m/s) / 4 s = 5 m/s². Work through similar problems in pairs, discussing the steps taken to arrive at the solution.

Now, solve the following problems on your own: 1) A runner completes a 400 m lap in 50 seconds. Calculate their average velocity. 2) A car accelerates from 10 m/s to 30 m/s in 5 seconds. What is its acceleration? 3) Graph the motion of an object that moves with a constant velocity of 15 m/s for 10 seconds. Be prepared to share your solutions with the class.

• m/s
• m²/s
• kg
• N

Answer: m/s

Velocity is measured in meters per second (m/s), which indicates the distance traveled in meters for each second.

• Speed
• Distance
• Displacement
• Time

Answer: Displacement

Displacement is a vector quantity because it has both magnitude and direction, unlike speed and distance.

Answer: Acceleration is the rate of change of velocity over time.

Acceleration measures how quickly an object changes its velocity, indicating whether it is speeding up or slowing down.

• It is increasing
• It is decreasing
• It is zero
• It is negative

Answer: It is zero

When an object moves with constant velocity, it does not change its speed or direction, resulting in zero acceleration.

Answer: Average velocity = total displacement / total time.

This formula allows us to find the average velocity by dividing the total change in position by the total time taken.

• 25 m/s
• 20 m/s
• 15 m/s
• 10 m/s

Answer: 25 m/s

Average speed is calculated as total distance divided by total time. Here, 100 m / 4 s = 25 m/s.

• Constant speed
• Acceleration
• No movement
• Deceleration

Answer: No movement

A flat line on a distance-time graph indicates that the object is not changing its position over time, meaning it is at rest.