Question

1. what is the difference between speed and velocity?
2. when would the velocity and acceleration of an object be in the same direction? if was constantly going in same direction
3. when would the velocity and acceleration of an object be in opposite directions?
4. if a ball is thrown straight into the air, what would the velocity be at the top of its trajectory?
5. your car has a device that tells you how fast you are traveling. why is this device a speedometer instead of a velocitymeter?

Explanation:

1. Speed is a scalar quantity representing how fast an object is moving, while velocity is a vector quantity that includes both speed and direction.
2. When an object is moving with constant speed in a straight - line path (constant velocity), its acceleration is zero as there is no change in velocity.
3. When an object is slowing down, its acceleration is in the opposite direction of its velocity. For example, a car braking has acceleration opposite to its motion direction.
4. At the top of the trajectory of a ball thrown straight up, the ball momentarily stops before falling back down. So its velocity is 0 m/s.
5. A speedometer measures speed because it only gives information about how fast the car is moving and does not account for the direction of motion. Velocity requires both magnitude (speed) and direction, and a car's speed - measuring device does not provide directional information.

Answer:

1. Speed is a scalar (magnitude only), velocity is a vector (magnitude and direction).
2. When moving with constant velocity (constant speed in a straight - line).
3. When the object is slowing down.
4. 0 m/s.
5. Because it only measures the magnitude of the rate of motion (speed) and not the direction (which is needed for velocity).