Motion

__________ is the ratio of the distance an object moves to the amount of time the object moves.

The base SI units for speed are __________. *Use the abbreviations for the units.

The equation for calculating average speed is __________. *Use the abbreviations for the variables.

You can determine how fast you were going at the midpoint on a trip by calculating average speed for the entire trip.

• True
• False

Answer explanation

Average speed only takes into account the total distance when calculated, and cannot be used to measure speed at any given moment in time.

A student walked 1.5 km in 15 minutes, and then, realizing he was late, ran the remaining 0.5 km in 5 minutes. What is his average speed on the way to school? *Use the abbreviation of the unit(s).

The type of speed an automobile's speedometer displays is called __________ speed.

Answer explanation

Instantaneous speed is the rate at which an object is moving at a given moment in time.

Velocity can also be described as speed with __________.

Answer explanation

Velocity is the speed and direction an object is moving, measured relative to a reference point.

Which of these examples describes a change in velocity.

• a moving object gains speed
• a moving object changes direction
• a moving object moves in a straight line at a constant speed
• a moving object slows down

Answer explanation

A change in velocity can only occur if there is a change in speed and/or direction.

If a car travels around a gentle curve on a highway at 60 km/h, the velocity does not change.

• True
• False

Answer explanation

An object can change its velocity if it changes its speed and/or direction.

A river flows at a velocity of 3 km/h downstream relative to the riverbank. A boat moves upstream at a velocity of 15 km/h relative to the riverbank. What is the velocity of the boat relative to the riverbank?

• 18 km/h downstream
• 15 km/h upstream
• 12 km/h upstream
• 12 km/h downstream

Answer explanation

The velocities combine by vector addition to determine the true velocity of an object.