Physics - Term 2 - Week 7

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 the movement along a straight line. Displacement is the change in position of an object and is a vector quantity, meaning it has both magnitude and direction. Distance, on the other hand, is a scalar quantity that refers to the total path length traveled. Velocity is defined as the rate of change of displacement and can be calculated as the change in position divided by the time taken. Acceleration is the rate of change of velocity and can be positive (speeding up) or negative (slowing down).

Consider a car that travels 100 meters east in 5 seconds and then returns 40 meters west in 2 seconds. To find the total displacement, we calculate the net change in position: Displacement = 100 m (east) - 40 m (west) = 60 m (east). To find the average velocity, we divide the total displacement by the total time taken: Total time = 5 s + 2 s = 7 s. Average velocity = Displacement / Time = 60 m / 7 s ≈ 8.57 m/s (east).

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, and the final velocity is 20 m/s. Thus, 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.

1. A car travels 150 meters in 3 seconds. Calculate its average speed. 2. An object is thrown upwards with a velocity of 15 m/s. How long will it take to reach its highest point? (Use g = 9.8 m/s²). 3. A runner accelerates from 0 to 10 m/s in 5 seconds. What is the runner's acceleration? Solve these problems and be prepared to discuss your answers in class.

• Total distance traveled
• Change in position
• Speed in a given direction
• Rate of change of velocity

Answer: Change in position

Displacement is defined as the change in position of an object and is a vector quantity.

• Velocity
• Acceleration
• Distance
• Displacement

Answer: Distance

Distance is a scalar quantity that refers to the total path length traveled, without direction.

• It is increasing
• It is decreasing
• It is zero
• It is constant

Answer: It is zero

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

Answer: 8 m/s

Average speed = Total distance / Total time = 400 m / 50 s = 8 m/s.

Answer: Acceleration = (Final velocity - Initial velocity) / Time

This formula calculates how quickly an object's velocity changes over time.

• 2 m/s²
• 5 m/s²
• 10 m/s²
• 3 m/s²

Answer: 2 m/s²

Acceleration = (20 m/s - 10 m/s) / 5 s = 2 m/s².

Answer: 2.04 seconds

Time to reach peak = Initial velocity / g = 20 m/s / 9.8 m/s² ≈ 2.04 seconds.