What two controls on a car cause a change in speed? What control causes only a change in velocity?

In a car, the two controls that primarily cause a change in speed are the accelerator pedal and the brake pedal.

1. Accelerator Pedal: When the driver presses the accelerator, the engine receives more fuel and air, increasing the car's speed. This control directly affects how fast the car is moving.

2. Brake Pedal: When the driver presses the brake pedal, it engages the braking system, which reduces the speed of the car. This action slows down the vehicle or brings it to a stop.

In terms of changing only the velocity, which is a vector that includes both speed and direction, the steering wheel is the relevant control. When a driver turns the steering wheel, they change the direction of the vehicle while the speed can remain constant, thus causing a change in velocity due to the change in direction. This demonstrates that while speed may not change, the vector representation of velocity does.