# Newton’s laws of motionPage 9

#### WATCH ALL SLIDES

When lift is greater, the helicopter

A. climbs down.

climbs up.

hovers in midair.

None of the above

Newton’s Third Law

Slide 69

When lift is greater, the helicopter

A. climbs down.

climbs up.

hovers in midair.

None of the above

Newton’s Third Law

Slide 70

A bird flies by

A. flapping its wings.

pushing air down so that the air pushes it upward.

hovering in midair.

inhaling and exhaling air.

Newton’s Third Law

Slide 71

A birds flies by

A. flapping its wings.

pushing air down so that the air pushes it upward.

hovering in midair.

inhaling and exhaling air.

Newton’s Third Law

Slide 72

Slightly tilted wings of airplanes deflect

A. oncoming air downward to produce lift.

oncoming air upward to produce lift.

Both of these.

Neither of these.

Newton’s Third Law

Slide 73

Slightly tilted wings of airplanes deflect

A. oncoming air downward to produce lift.

oncoming air upward to produce lift.

Both of these.

Neither of these.

Explanation:

When a wing diverts air downward, it exerts a downward force on the air. The air simultaneously exerts an upward force on the wing. The vertical component of this upward force is lift. (The horizontal component is drag.)

Newton’s Third Law

Slide 74

Compared with a light-weight glider, a heavier glider would have to push air

A. downward with greater force.

downward with the same force.

downward with less force.

none of the above

Newton’s Third Law

Slide 75

Compared with a light-weight glider, a heavier glider would have to push air

A. downward with greater force.

downward with the same force.

downward with less force.

none of the above

Explanation:

The force on the air deflected downward must equal the weight of the glider.

Newton’s Third Law