Centripetal and Centrifugal Forces

Instructions: answer the questions, check them carefully, and when you are sure they are all right, press submit. The number of correct answers will be displayed.

Question 1: In science fiction, spaceships are often made in the shape of a large wheel. Why is this?

To help move into a faster or higher orbit

The wheel provides more space

To create artificial gravity

To make sure the spacecraft does not heat too much on one side

So that the astronomers can see all of the sky

Question 2: In the image of a joyride, a wheel rotates, causing the passengers to move out to the sides. If the supporting ropes were to break suddenly, in which direction would the people go ?

They would fly outwards in a spiral

Straight out away from the centre

They would fall towards the centre of the wheel because the centripetal force is real and the centrifugal force is not real

In a straight line at a tangent to the circular path

Question 3: Why do scientists do thought experiments?

Because practical experiments do not always get the results they want

To demonstrate a principle

To save time and money on expensive equipment

Question 4: What did David Scott prove when he dropped a hammer and a feather on the Moon?

Feathers weigh as much as hammers in low-gravity

That Galileo was right, and there is gravity on the Moon

All objects fall at the same constant speed

That it is air resistance that confuses results on Earth

Question 5: Newton's cannonball thought experiment is so famous because:

It led to the invention of satellites

Without it we would never have had gravity and orbits

It proved to be correct centuries later

It illustrated a principle that people found difficult to comprehend otherwise

Question 6: Projectiles with horizontal velocities fall at the same acceleration as objects with no horizontal velocity. They all reach the surface at the same time, irrespective of their initial speed. Why then does Newton's cannonball not reach the Earth?

The Earth is also moving

It is only a thought experiment - in a real experiment it wold reach the surface

The Earth is round

Question 7: Why are the Moon and all the planets moving?

Gravity of the Sun makes them move faster if they slow down

They are not - their motion is an illusion caused by Relativity

They have an angular velocity from the time of their formation, 6 billion years ago

Question 8: What do you call the time it takes a satellite to travel once around a planet?

period

ellipse

orbit

circumnavigation

Question 9: Why are a lot of satellites placed in geosynchronous orbit?

To avoid the need to readjust their position continuously

To avoid colliding with faster moving satellites

To avoid low-flying space junk

To provide continuous coverage over one area on Earth

Question 10: Why aren't manned space stations in geosynchronous orbits?

It would be too expensive to go so far

Radio signals are too weak so far away

Manned stations need to be closer and moving around the Earth to see more

Gravity is too weak up there for humans to survive for long periods

They are in geosynchronous orbit

Question 11: Why is it better to fire a projectile at 45° to the horizontal than horizontally?

Projectiles travel faster at this angle

It is more accurate

45° gives the longest range

To form a parabolic trajectory

Question 12: If an astronaut fired a projectile from his space station in the opposite direction to his motion, what would happen?

The projectile would travel around the Earth and hit him in 90 minutes time

The projectile would enter a higher orbit

The projectile would enter a lower orbit

The projectile would follow the space station

Question 13: What causes a book to slide on a car seat, when the car goes around a bend?

velocity

centripetal force

centripetal acceleration

friction

inertia

Question 14: What keeps the Moon in orbit around the Earth?

centripetal acceleration

tangential velocity

centripetal force

centrifugal force

Question 15: How fast does Jupiter move in its orbit?

Faster than Earth and Saturn

Slower than Earth and Saturn

Slower than Earth but faster than Saturn

Faster than Earth but slower than Saturn

Question 16: Satellite A is in orbit around the Earth at 500km altitude. Satellite B is in orbit at 1000km. What can be said of their velocities?

Sat A is travelling faster than Sat B

Sat A is travelling slower than Sat B

Sat A is travelling half as fast as Sat B

Sat A is travelling four times as fast as Sat B

Sat A is travelling twice as fast as Sat B

Question 17: Which of these planets is travelling fastest in orbit?

Mars

Earth

Venus

Mercury

Question 18: A car has an antenna pointing straight up. When it goes around a corner, which direction does the top of the antenna bend?

outwards

towards the centre of curvature

forwards

backwards

Question 19: Why do motocyclists lean over when they go around a bend?

so they can 'fall' into the centre of the circle

to make them go faster around the bend

so their weight counterbalances the centrifugal effect

the round wheels force them over

Question 20: A 60kg lady experiences 4g on a roller coaster bend. What is the force on her?

15 N

60 N

240 N

2400 N