Physics 20 AM GROUP only Week 7 Summative TaskDue May 22nd .

Please try to stay in the time constraints from the Weekly Plan. If it is taking you too lone, please contact me. You may skip over some questions if time is an

issue, so you get some of each type done

THE FOLLOWING MATERIAL IS FOR WEEK 6, THE PREVIOUS WAS FROM WEEK 5 MATERIAL

Centripetal Motion1. List the three equations for centripetal motion and list their variables

2. If an object is moving in a circle at a constant speed, is it accelerating? How do you know?

3. What direction is the velocity acting for circular motion?

4. What direction is the acceleration acting for circular motion?

5. What is the period of a yoyo spinning at 14.4m/s in a 1.3m circle?

6. What is the acceleration acting on a child being swung in a circle by a parent in a helicopter ride if they make 4 spins in 1.1s with a radius of 1.8m?

7. A roller coaster ride goes around a 12.5m radius curve and the rider experiences an acceleration of 15.2m/s2. How fast were they going?

8. An airplane pilot experiences an acceleration of 26.9m/s2 when banking at 315m/s. What is the radius of the curve she is trying to make?

Centripetal ForceCentripetal force is the NET FORCE acting on an object to keep it moving in a circle. It can be caused by friction, gravity, normal force, tension, or any combination of them. Since Fnet is simply mass times acceleration, centripetal force is mass time centripetal acceleration.

Show all givens, equations, work and units in your problem solving. Be sure to show an Fnet diagram for circular motion.

1. What force is needed to cause an electron moving 4.5 x 105m/s, with a mass of 9.11 x 10-31kg, to spin in a circle with a radius of 85cm?

2. A 350g yo-yo is swung in a horizontal circle. If the force needed to break the 2.0m string is 15N, what velocity does the yo-yo need to be swung to break the string?

3. A 1150kg car goes around a bank in the road with a radius of 29.0m at 75km/h. What is the force of friction (solve for centripetal force) required to keep it from sliding off the road?

4. A 1250N force keeps an 80kg object going in a circle with a radius of 145cm. How long does it take to make one revolution?

5. The 2600kg Batmobile is travelling 125km/h around a curve of what radius if it requires 70 000N of force to stay in circular motion.

THE FOLLOWING MATERIAL IS FOR WEEK 7, THE PREVIOUS WAS FROM WEEK 6 MATERIAL

Universal Law of GravitationGravity is known to be the pull of any objects with mass towards any other objects with mass. We most often look at it as our experience of being pulled towards the earth. We don’t often consider our attraction to the lamp on our desk, the pear in our lunch, the chair we sit on, or a car driving past. Usually this is because the gravity from the massive earth is so strong that all other gravitational forces aren’t noticed.

Things to note, any two objects with mass are attracted by gravity.

No matter what the two objects size or masses are, the gravitational forces are equal (Newton’s third law)

We often use the shortcut when we are on the surface of the earth where gravity is 9.81m/s2. But this only works on the surface of the earth where we can use Fg=mg

The true equation for gravity is called the Universal Law of Gravitation

Gravity is an attractive force only. It is normally very weak, but if you have very large masses like planets, stars, etc it can be strong and act over large distances

Cavendish studied the relationship between distance and force to come up with the equation and solve for the universal gravitational constant G. When solving for radius it is from the center to center of the objects.

ALL FORCE QUESTIONS MUST HAVE A FBD

1. Find the force of gravity (weight) of a 100kg object on the surface of the earth (6.37 x 106m, which has a mass of 5.97x1024kg) using:

a. F=mgb. F=Gmm/r2

2. Find the attraction (of gravity) between Goofy (80kg) and Micky Mouse (65kg) if they are 2.5m apart.

3. Find the force of gravity acting on a 3000kg satellite 45km above the surface of the Earth. (note: above the surface means add the radius of the earth to the height to get the radius)

4. Find the distance between two masses, 85kg and 120kg that have a force of attraction of 8.6 x 10-7N

5. What happens to the force of gravity when both masses triple and the radius doubles.

6. Find the force of gravity between the sun and the Earth. You will need to look up values online.

Cavendish experimentally determined the relationship between the force acting on two masses and the radius between them. Using the following experimental results complete the following:

a. graph a Fg vs r graph (5)Radius (cm) Force (x 10-7 N)

10 480

20 120

30 52

40 33

50 19

60 13

70 11

80 7

Kepler’s Laws

Kepler was an astronomer who helped to shape our understanding of how planets moved in our solar system. His model is based on three principles discovered through many years of study and following the motion of the planets.

1st Law:

Planets follow elliptical orbits, not circular. These orbits have 2 foci, one of them is the sun and the other a point in space.

2nd Law:

For equal amounts of time, the area that the planets open up between the sun and the partial circumference are equal. This means the closer to the sun, the faster you go.

3rd Law:

For any bodies with objects in orbit, there is a constant value k based on the relation of time and radius of orbits.

T2

=T2

r3 r3

This third law is very helpful in comparing two satellites orbiting the same celestial body.

Kepler Problem:

1. How much farther is Jupiter than the Earth if a year on Jupiter is 12 years?

Circular Motion and Gravitation (use constants from your data sheet)

(Fc=Fg) or (m4π2r/T2 = Gmm/r2)Problems:

1. Find the mass of Planet Batman if one of her moons orbits every 21day (each day on this planet is the same as a day on Earth), at a radius of 2.55 x 106m

2. What is the radius of the moons orbit around the earth if it takes 27.4 day to complete one orbit