Physics - Term 3 - Week 5

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 traveled. Velocity is defined as the rate of change of displacement, while speed is the rate of change of distance. Acceleration is the rate of change of velocity over time.

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

Let's work together on a problem: A cyclist increases their velocity from 5 m/s to 15 m/s in 4 seconds. To find the acceleration, we use the formula: acceleration = (final velocity - initial velocity) / time. Here, acceleration = (15 m/s - 5 m/s) / 4 s = 10 m/s / 4 s = 2.5 m/s². This exercise helps reinforce the concept of acceleration and how to calculate it using given values.

Now, try solving the following problem on your own: A car starts from rest and accelerates uniformly at 3 m/s² for 6 seconds. Calculate the final velocity and the distance traveled during this time. Use the equations: final velocity = initial velocity + (acceleration × time) and distance = (initial velocity × time) + (0.5 × acceleration × time²). This task will help you apply the kinematic equations to find both final velocity and distance.

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

Answer: Velocity includes direction, speed does not.

Velocity is a vector quantity, which means it has both magnitude and direction, while speed is a scalar quantity that only has magnitude.

• 10 m/s
• 100 m/s
• 0.1 m/s
• 1 m/s

Answer: 10 m/s

Average speed is calculated as total distance divided by total time. Here, 100 meters / 10 seconds = 10 m/s.

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.

• a = (v_f - v_i) / t
• a = (d_f - d_i) / t
• a = v_i + (at)
• a = d / t

Answer: a = (v_f - v_i) / t

Acceleration is defined as the change in velocity (final velocity minus initial velocity) divided by the time taken.

Answer: The unit of acceleration is meters per second squared (m/s²).

Acceleration measures how quickly velocity changes, hence the unit reflects a change in velocity over time.

• 6 m/s²
• 5 m/s²
• 10 m/s²
• 3 m/s²

Answer: 6 m/s²

Using the formula a = (v_f - v_i) / t, we have (50 m/s - 20 m/s) / 5 s = 30 m/s / 5 s = 6 m/s².