Question

1. does the speedometer of a car read average speed or instantaneous speed? how do you know? 2. if the speedometer of your car reads a constant speed of 40km/hr, can you say 100% for sure that the car has a constant velocity? explain your answer. 3. what two controls on a car cause a change in speed? 4. what control causes a change in velocity? 5. what is the acceleration of a car that travels in a straight line at a constant speed? 6. describe a situation in which you can accelerate even though your speed doesnt change.

Explanation:

Step1: Understand speedometer function

A speedometer measures the instantaneous speed of a car at a given moment. It doesn't measure average speed over a period.

Step2: Answer question 1

The speedometer of a car reads instantaneous speed. We know this because it gives the speed at each specific instant, not an average value over a distance or time - interval.

Step3: Understand velocity concept

Velocity is a vector quantity that has both magnitude (speed) and direction. Constant speed doesn't necessarily mean constant velocity if the direction changes.

Step4: Answer question 2

If the speedometer reads a constant speed of 40 km/hr, we cannot say 100% for sure that the car has a constant velocity. This is because the car could be changing direction (e.g., going around a circular track at a constant speed), and a change in direction means a change in velocity (since velocity is a vector).

Step5: Identify car - speed controls

The accelerator pedal and the brake pedal are two controls on a car that cause a change in speed. The accelerator increases speed and the brake decreases speed.

Step6: Understand velocity - change causes

A change in velocity can be caused by a change in speed or a change in direction. The steering wheel causes a change in direction (and thus can change velocity even if speed is constant), and the accelerator/brake cause a change in speed (which also changes velocity).

Step7: Understand acceleration with constant speed

Acceleration is the rate of change of velocity. If a car is moving in a straight - line at a constant speed, its acceleration is zero. But if it is moving in a circular path at a constant speed, it is accelerating because its direction is changing. For example, a car moving around a round - about at a constant speed is accelerating due to the change in direction of its velocity vector.

Answer:

1. The speedometer of a car reads instantaneous speed. We know this as it shows the speed at a particular moment, not an average over a period.
2. No, we cannot say 100% for sure that the car has a constant velocity. The car could be changing direction while maintaining a constant speed, and since velocity is a vector (has direction and magnitude), a change in direction means a change in velocity.
3. The accelerator pedal and the brake pedal are two controls on a car that cause a change in speed.
4. The steering wheel can cause a change in direction (and thus velocity) while the accelerator and brake can cause a change in speed (and thus velocity).
5. Yes, a car can accelerate even though its speed doesn't change if it is changing direction. For example, when a car moves in a circular path at a constant speed, it is accelerating because the direction of its velocity vector is changing.