Physics - Term 3 - Week 8

Kinematics is the branch of physics that describes the motion of objects. It focuses on quantities such as displacement, which is the change in position of an object, and is a vector quantity. Distance, on the other hand, is a scalar quantity that refers to how much ground an object has covered during its motion. Speed is the rate at which an object covers distance, while velocity is the speed of an object in a given direction. Acceleration is the rate of change of velocity and can be positive (speeding up) or negative (slowing down).

A car travels 100 meters east and then 50 meters west. To find the displacement, we consider the direction. The total displacement is 100 m (east) - 50 m (west) = 50 m (east). This shows how displacement takes direction into account, unlike distance.

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, we consider the net displacement as zero). Therefore, the average velocity is 0 m/s. Discuss with your partner how this differs from average speed, which would be 400 m / 50 s = 8 m/s.

A bicycle 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. Here, initial velocity is 0 m/s, final velocity is 20 m/s, and time is 5 s. Students should calculate the acceleration and reflect on how this relates to the bicycle's motion.

• Distance is a vector, displacement is a scalar.
• Distance is a scalar, displacement is a vector.
• Both are scalars.
• Both are vectors.

Answer: Distance is a scalar, displacement is a vector.

Distance measures the total path length, while displacement measures the shortest path between two points, considering direction.

• It is always positive.
• It can be negative.
• It is the same as speed.
• It does not have a direction.

Answer: It can be negative.

Velocity is a vector quantity and can be negative if the object is moving in the opposite direction.

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 is increasing.

Answer: It is zero.

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

Answer: Average speed = total distance / total time.

Average speed is calculated by dividing the total distance traveled by the total time taken.

• Its speed is increasing by 2 m/s every second.
• It travels 2 meters every second.
• It moves 2 meters in 2 seconds.
• It has a constant speed.

Answer: Its speed is increasing by 2 m/s every second.

An acceleration of 2 m/s² means the object's velocity increases by 2 m/s for every second of motion.