Physics - Term 1 - Week 4

Kinematics is the branch of physics that deals with the motion of objects without considering the forces that cause the motion. The three fundamental quantities in kinematics are displacement, velocity, and acceleration. Displacement is a vector quantity that refers to the change in position of an object. Velocity is the rate of change of displacement and is also a vector quantity. Acceleration, on the other hand, is the rate of change of velocity over time. Understanding these concepts is crucial for analyzing motion in one dimension.

Consider a car that travels 100 meters east and then 50 meters west. To calculate the total displacement, we take the initial position as zero. The car moves to +100 m and then back to +50 m. Therefore, the displacement is 100 m - 50 m = 50 m east. This example illustrates how to calculate displacement by considering the direction of movement.

Let's calculate the average velocity of a runner who completes a 400-meter lap in 50 seconds. The average velocity can be calculated using the formula: velocity = displacement / time. Here, the displacement is 400 meters (since the runner returns to the starting point) and the time is 50 seconds. Thus, the average velocity is 400 m / 50 s = 8 m/s. Discuss with your partner how the direction of motion affects the velocity.

Now, try solving the following problems on your own. A car accelerates from rest to a speed of 20 m/s in 5 seconds. Calculate the acceleration using the formula: acceleration = (final velocity - initial velocity) / time. Additionally, consider a scenario where a ball is thrown upwards with an initial velocity of 15 m/s. Determine how long it takes for the ball to reach its highest point.

• Meters
• Seconds
• Kilograms
• Newtons

Answer: Meters

Displacement is measured in meters, which is the standard unit of length in the International System of Units (SI).

• Distance over time
• Displacement over time
• Acceleration over time
• Force over mass

Answer: Displacement over time

Velocity is defined as the rate of change of displacement with respect to time, making it a vector quantity.

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

Acceleration indicates how quickly an object is speeding up or slowing down.

• It is positive
• It is negative
• It is zero
• It varies

Answer: It is zero

Constant velocity means there is no change in speed or direction, hence the acceleration is zero.

Answer: Average velocity = Displacement / Time

This formula allows you to find the average velocity of an object over a specific time interval.

• 30 m/s
• 25 m/s
• 20 m/s
• 15 m/s

Answer: 30 m/s

Average speed is calculated as total distance divided by total time, which is 150 m / 5 s = 30 m/s.

• It remains constant
• It decreases
• It increases
• It becomes zero

Answer: It increases

In free fall, the only force acting on the object is gravity, causing its velocity to increase as it falls.