Question 1

When a car is driving along a flat road and not skidding, the friction between the tires and the road is typically:

Accepted Answer

Static friction, because the contact point is momentarily at rest relative to the road.

Question 2

A car rounds a flat curve of radius $$r at $$constant speed $$v. $$What provides the necessary centripetal force to keep the car moving in a circle?

Accepted Answer

The static friction force between the tires and the road.

Question 3

If a car is moving too fast around a flat curve and begins to skid, what happens to the frictional force?

Accepted Answer

It decreases because kinetic friction is smaller than static friction.

Question 4

On a banked curve with no friction, the ideal speed $$v$$ for a car to make the turn of radius $$r at $$angle $$	heta is $$given by:

Accepted Answer

$$v = \sqrt{g r 	an 	heta}$$

Question 5

A car rounds a banked curve without skidding. The direction of the friction force on the tires depends on:

Accepted Answer

The speed of the car relative to the ideal speed for the bank angle.

Question 6

If an object moves in a circular path at varying speed, its acceleration:

Accepted Answer

Has both radial and tangential components.

Question 7

The drag force on an object moving through a fluid at low speeds is approximately:

Accepted Answer

Proportional to the velocity.

Question 8

The terminal velocity $$v_T of a $$falling object experiencing a drag force proportional to velocity is:

Accepted Answer

$$v_T = \frac{mg}{b}$$

Question 9

According to Newton’s Law of Universal Gravitation, the gravitational force between two masses $$m_1$$ and $$m_2$$ separated by distance $$r is$$:

Accepted Answer

$$F = G \frac{m_1$ m_2$}{r^2$}$$

Question 10

Which is stronger, Earth’s pull on the Moon, or the Moon’s pull on Earth?

Accepted Answer

They pull on each other equally.

Question 11

A particle is placed inside a thin spherical shell of mass $$M$$ and radius $$R. $$The net gravitational force on the particle is:

Accepted Answer

Zero

Question 12

If you weigh yourself at the equator of Earth, would you get a larger, smaller, or similar value than if you weigh yourself at one of the poles?

Accepted Answer

Smaller value

Question 13

A satellite in low Earth orbit is said to be 'weightless.' What is the best explanation for this?

Accepted Answer

The satellite and its contents are in free fall, so there is no normal force.

Question 14

Kepler’s third law, as derived from Newton’s law of gravitation for a planet of mass $$m$$ orbiting a star of mass $$M at $$distance $$s$$, is:

Accepted Answer

$$T^2$$ = \frac{4\$$pi^2$$}{GM} $$s^3$$

Question 15

A planet of mass $$m is a $$distance $$d$$ from Earth. Another planet of mass $$2m is a $$distance $$2d$$ from Earth. Which planet exerts a greater gravitational force on Earth?

Accepted Answer

The planet of mass $$m at $$distance $$d.$$

Question 16

The acceleration due to gravity $$g at $$the surface of the Earth is given by:

Accepted Answer

$$g = G \frac{m_E}{r_E^2$}$$

Question 17

The flight path of the 'Vomit Comet' airplane to produce microgravity is:

Accepted Answer

A parabola

Question 18

As a planet gets closer to the Sun in its elliptical orbit, the magnitude of its velocity:

Accepted Answer

Speeds up

Question 19

From what location on Earth is it easiest to launch a rocket into orbit, and why?

Accepted Answer

The Equator, because the rotational speed of Earth adds to the rocket's velocity.

Physics Study Guide: Gravitation, Friction, and Orbits

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