physics ch 3 quiz

How does a vector quantity differ from a scalar quantity?

a vector quantity has both magnitude and direction , a scalar quantity has magnitude only

Why is speed classified as a scalar quantity and velocity classified as a vector quantity?

speed is a scalar because it has magnitude only, velocity is a vector because it has magnitude and direction

If a vector that is 1 cm long represents a velocity of 10 km/h, what velocity does a vector 2 cm long drawn to the same scale represent?

20 km/h

When a rectangle is constructed in order to add velocities, what represents the resultant of the velocities?

the diagonal of the rectangle

Why do we say that a rectangle is a special case of a parallelogram?

because all four angles are right angles.

Will a vector at 45° to the horizontal be larger or smaller than its horizontal and vertical components? By how much?

each component is smaller than the vector. each component is about 0.707 times the vector, so the vector is about 1.414 times either component.

Why does a bowling ball move without acceleration when it rolls along a bowling alley?

it has no horizontal acceleration

In the absence of air resistance, why does the horizontal component of velocity for a projectile remain constant while the vertical component changes?

gravity acts only downward, so the horizontal velocity remains constant while the vertical velocity changes

How does the downward component of the motion of a projectile compare with the motion of free fall?

the downward component of a projectile’s motion is the same as the motion of free fall.

At the instant a ball is thrown horizontally over a level range, a ball held at the side of the first is released and drops to the ground. If air resistance is neglected, which ball strikes the ground first?

both balls strike the ground at the same time because horizontal motion does not affect how quickly they fall

How far below an initial straight-line path will a projectile fall in one second?

(d=½ gt² ) (d= ½ (10)(1² )) (d = 5 m)

At what angle should a slingshot be oriented for maximum altitude? For maximum horizontal range?

maximum altitude: 90°

maximum horizontal range: 45°

Neglecting air resistance, if you throw a ball straight up with a speed of 20 m/s, how fast will it be moving when you catch it?

20 m/s

Neglecting air resistance, if you throw a baseball at 20 m/s to your friend who is on first base, will the catching speed be greater than, equal to, or less than 20 m/s?

the catching speed will be equal to 20 m/s.

Does the speed change if air resistance is a factor?

yes. the catching speed will be less than 20 m/s because air resistance slows the ball down.

What do we call a projectile that continually “falls” around Earth?

a satellite

How fast must a projectile moving horizontally travel so that the curve it follows matches the curve of Earth?

about 8 km/s, or about 18,000 mi/h

Why is it important that such a satellite be above Earth’s atmosphere?

so atmospheric friction does not slow it down

What force acts on a satellite that is above Earth’s atmosphere?

gravity.