Physics - Term 2 - Week 8

Kinematics is the branch of physics that deals with the motion of objects without considering the forces that cause the motion. In one-dimensional motion, we focus on how an object moves along a straight line. Key terms include displacement, which is the change in position of an object, and distance, which is the total path length traveled. Velocity is defined as the rate of change of displacement, while speed is the rate of change of distance. Understanding these concepts is crucial for analyzing motion.

Consider a car that travels 150 meters to the east in 5 seconds. To find the average velocity, we use the formula: average velocity = displacement / time. Here, the displacement is 150 meters and the time is 5 seconds. Thus, average velocity = 150 m / 5 s = 30 m/s to the east. This example illustrates how to apply the definition of average velocity in a practical scenario.

Let's work through a problem together. A cyclist 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. Here, the initial velocity is 0 m/s, the final velocity is 20 m/s, and the time is 4 seconds. Therefore, acceleration = (20 m/s - 0 m/s) / 4 s = 5 m/s². Now, try calculating the acceleration if the cyclist reaches 30 m/s in 6 seconds.

Now it's your turn to apply what you've learned. Solve the following problems: 1) A car starts from rest and accelerates uniformly at 2 m/s² for 10 seconds. What is its final velocity? 2) A ball is thrown upwards with an initial velocity of 15 m/s. How high will it rise before it starts to fall back down? Use the kinematic equations to find the answers and be prepared to discuss your solutions.

• Speed is a vector, velocity is a scalar.
• Speed is a scalar, velocity is a vector.
• Both are the same.
• Speed includes direction, velocity does not.

Answer: Speed is a scalar, velocity is a vector.

Speed only has magnitude, while velocity has both magnitude and direction.

Answer: Displacement is the change in position of an object, measured as a straight line from the initial to the final position.

Displacement considers only the initial and final positions, not the path taken.

• 5 m/s
• 10 m/s
• 15 m/s
• 20 m/s

Answer: 10 m/s

Average speed is calculated as total distance divided by total time: 100 m / 10 s = 10 m/s.

Answer: Acceleration = (final velocity - initial velocity) / time.

This formula shows how acceleration is the change in velocity over time.

• Distance
• Speed
• Displacement
• All of the above

Answer: Displacement

Displacement is a vector quantity as it has both magnitude and direction.

Answer: Uniform acceleration means that an object's velocity changes at a constant rate over time.

In uniform acceleration, the acceleration remains the same throughout the motion.

• 20 m/s east
• 20 m/s west
• 200 m/s east
• 200 m/s west

Answer: 20 m/s east

Average velocity is calculated as displacement divided by time: 200 m / 10 s = 20 m/s east.