Unit 4 Test - Gravitation, Circular Motion and Astronomy

The gravitation force involves two masses, and their force is ALWAYS...

• Equal magnitude and opposite direction

• Equal magnitude and same direction

• Different magnitude and opposite direction

• Different magnitude and same direction

If the distance "r" double, what happens to the force?

• It doubles (multiplied by 2)

• It goes down to half (divided by 2)

• It goes down to a quarter (divided by 4)

• It quadruples (multiplied by 4)

An asteroid with a mass of 

 $4\times10^{21}$  kg feels a gravitational pull from an adjacent asteroid with a mass of $2\times10^{21}$  kg. If they are 1000 m away from each other, what is the gravitational force?

•  $8.01\times10^{26}\ N$  

•  $5.34\times10^{29}\ N$  

•  $5.34\times10^{26}\ N$  

The greater the period of an orbit, the ____ the velocity.

• Greater

• Smaller

When the Earth is in motion around the Sun, which of the following vectors are pointed towards the center of the orbit? [More than one to select]

• Velocity

• Centripetal Force

• Acceleration

• Centrifugal Force

• Mass

A wild and crazy dog runs a circular loop around a cat. If the cat sits in the center with a radius of 3 m, and if the dog is running at 6 m/s, what is the acceleration of the dog's "orbit?"

• $12\ \frac{m}{s^2}$

  
  

• $36\frac{m}{s^2}$

• 2 $\frac{m}{s^2}$

• 1.5 $\frac{m}{s^2}$

A 9 kg tire rotates around the wheel of a car with a radius of 0.19 m. If the tire has a speed of 16 m/s, what is the centripetal force that keeps the tire spinning on the wheel?

• 6,821.1 N

• 757.9 N

• 12,126.3 N

• 1,347.4 N

Which force is acting as the centripetal force when a car makes a sharp turn around a curve?

• Gravitational

• Friction

• Normal

• Applied

When the Moon orbits around the Earth, what prevents the Moon from just flying off into the distance in a straight line?

• Newton's First Law/Inertia

• Gravitational Force

• Velocity

• Friction Force

When the Moon orbits around the Earth, what prevents the Moon from stopping its motion and colliding into the Earth?

• Newton's First Law/Inertia

• Gravitational Force

• Velocity

• Friction Force