Physics - Term 1 - Week 3

Kinematics is the branch of physics that deals with the motion of objects without considering the forces that cause the motion. The three fundamental concepts in kinematics are 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 defined as 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).

A car travels 100 meters to the east and then 50 meters to the west. To find the total displacement, we consider the direction. The displacement is 100 m (east) - 50 m (west) = 50 m (east). This example illustrates how to calculate displacement by considering the direction of motion.

Consider a runner who completes a 400-meter lap in 50 seconds. To find the average velocity, we use 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 classmates how this average velocity differs from instantaneous velocity.

Solve the following problems on your own: 1) A car accelerates from rest to a speed of 20 m/s in 5 seconds. Calculate the acceleration. 2) An object moving at 15 m/s comes to a stop in 3 seconds. What is the acceleration? Write down your answers and be prepared to discuss your methods.

• 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).

• Change in velocity over time
• Distance traveled over time
• Speed in a given direction
• Total distance covered

Answer: Change in velocity over time

Acceleration is defined as the rate of change of velocity with respect to time.

Answer: Velocity is the rate of change of displacement with respect to time and includes both speed and direction.

Velocity is a vector quantity, meaning it has both magnitude (speed) and 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, hence the acceleration is zero.

Answer: Average velocity = total displacement / total time.

This formula gives the average velocity over a time interval based on the total displacement.

• 15 km/h
• 30 km/h
• 60 km/h
• 10 km/h

Answer: 15 km/h

Average speed is calculated as total distance divided by total time: 30 km / 2 h = 15 km/h.

• A straight line on a distance-time graph
• A straight line on a velocity-time graph
• A curved line on a distance-time graph