PHS ch 4 quiz

Why do the two objects hit the table at the relative times that they do?

Gravity pulls the same amount on both, and they both drop the same distance.

Find the height reached by the ball

gt^2/8

What would be your weight from its present value?

.25

What would be the mass of an object on Jupiter if the object has a mass of 1.7 kg on Mars

1.7 kg

A satellite at a particular point along an elliptical orbit has a gravitational potential energy of 5400 MJ with respect to earths surface and a kinetic energy of 4800 MJ. Later in its orbit the satellites potential energy is 5500 MJ

4700 MJ

From greatest to least rank the KEs of the balls when tossed

A=b=c

From greatest to least rank the initial PE's of the balls relative to the ground below

A=b=c

From greatest to least rank the times of flight while airborne

B a c

Rank the gravitational forces from greatest to least between (a) the sun and Mars (b) the sun and the moon and (c) the sun and earth

C a b

The dashed lines show three circular orbits abt earth. Rank from greatest to least their times to orbit earth

C b a

Suppose you are in an elevator. As the elevator starts upward, it's speed will increase. During this time when the elevator is moving upward with increasing speed your weight will be

Greater than your normal weight

Earth is farther away from the sun in June and closest in December. In which of these two months is earth moving faster around the sun

The Earth travels faster about the Sun in December than in June.

Which ball (if either) has the greatest speed at the moment of impact?

The ball thrown horizontally

A park ranger wants to shoot a monkey hanging from a branch of a tree with a tranquilizer dart. The ranger aims directly at the monkey not realizing that the dart will follow a parabolic path and thus will fall below the monkey. The monkey however sees the dart leave the gun and lets go of the branch to avoid being hit. Will the monkey be hit anyway? Does the velocity of the dart affect your answer assuming that it is great enough to travel the horizontal distance to the tree before hitting the ground? Defend your answer

The monkey will be hit by the dart. This will occur bc the dart and the monkey are both falling at the same rate which is gravity. As long as the velocity will cover the horizontal distance the specific magnitude does not matter. The velocity does affect the answer because if it is fast enough it will hit the monkey

How does the range of the pumpkin change of its initial velocity is tripled?

The pumpkins range is nine times as far

So far in this tutorial you have been launching a pumpkin. Let's see what happens to the trajectory if you launch something bigger and heavier like a car. Compare the trajectory and range of the pumpkin to that of the car using the same initial speed and angle

The trajectories and thus the range of the car and the pumpkin are identical

Based on the figure for which trajectory was the pumpkin in the air for the greatest amount of time

Trajectory A

Would the springs inside a bathroom scale be more compressed or less compressed if you weighed yourself in an elevator that accelerated upward? Accelerated downward?

Upward more compressed downward less compressed

If the ball reached the same height as when tossed at some angle would the time of flight be the same

Yes

Suppose you are in an elevator that is moving upward. As the elevator nears the floor at which you will get off its speed slows down. During this time when the elevator is moving upward with decreasing speed your weight will be

less than your normal weight at rest

If you are standing on a scale in an elevator, what exactly does the scale measure?

the force you exert on the scale

When the pumpkin is shot straight upward with an initial speed of 14 m/s what is the maximum height above its initial location?

10 m

What would be the weight of an object on Jupiter if the object weighs 1.7 lbs on Mars?

11 lb

If the ball is in the air for 3.4 s find a height it reaches

14 m

When dr. Hewitt releases the two projectiles which one hits the ground first

Both balls hit the ground at the same time.

What happens to the trajectory of the cannonball when you increase the diameter while keeping the mass constant?

Increasing the size makes the range of the trajectory decrease

If the initial speed of the pumpkin is doubled how does the maximum height change?

The maximum height increases by a factor of four

Consider Earth and the Moon. As you should now realize, the gravitational force that Earth exerts on the Moon is equal and opposite to that which the Moon exerts on Earth. Therefore, according to Newton's second law of motion __________.

the Moon has a larger acceleration than Earth, because it has a smaller mass

Calculate the force of gravity on the 1.4 kg mass of it were 1.9x10^7 m above earths surface

.85

Drag the cannon downwards so it is at ground level or 0 m then fire the pumpkin straight upward with an initial speed of 14 m/s. How long does it take for the pumpkin to hit the ground

2.8 s

If a space vehicle circled earth at a distance equal to the earth moon distance how long would it take for it to make a complete orbit? In other words, what would be its period?

28

Now lets see what happens when the cannon is high above the ground. Click on the cannon and drag it upward as far as it goes. Set the initial velocity to 14 m/s and fire several pumpkins while varying the angle. For what angle is the range the greatest?

30

Consider the video you just watched. Suppose we replace the original launcher with one that fired the ball upward at twice the speed. We make no other changes. How far behind the cart will the ball land compared to the distance in the original experiment

4 times as far

Erase all the trajectories and fire the pumpkin vertically again with an initial speed of 14 m/s. As you found earlier the maximum height is 9.99 m. If the pumpkin isn't fired vertically but at an angle less than 90° it can reach the same maximum height of its initial speed is faster. Set the initial speed to 22 m/s and find the angle such as the maximum height is roughly the same. Expert by firing the pumpkin with many different angles. What is this angle?

40°

The dashed lines show three circular orbits abt earth. Rank from greatest to least their orbital speeds

A b c

From greatest to least rank the KEs of the balls when they hit the ground below

A=b=c

In the previous part you found that a pumpkin fired with an initial speed of 22 m/s and an angle of 40° reaches the same height as a pumpkin fired vertically with an initial speed of 14 m/s which pumpkin takes longer to land

Both pumpkins are in the air abt the same time

What was the cause for f perturbations discovered in the orbit of planet Uranus?

Gravitational pulls from neptune

Consider an object of mass 45 kg. Rank the weight of this object at the following locations

Heaviest: Jupiter earth Saturn Mars moon lightest

A small light source located 1 m in front of a 1-m^2 opening illuminates a wall behind. If the wall is 1 m behind the opening the illuminated area covers 4 m^2. How many sq meters are illuminated if the wall is 3 m from the light source? 5 m? 10 m?

If it's 3 then it's 9m^2 if it's 5 then it's 10 m^2 if it's 10 then it's 100 m^2

A satellite can orbit at 5km above the moon, but not a 5km above earth. Why?

It can't orbit at 5 km above earth's surface bc there is too much air resistance. The earths atmosphere would slow down the satellite but since the moon has no atmosphere it can be launched at any altitude

An apple falls because of the gravitational attraction to earth. How does the gravitational attraction of earth to the apple compare?

The attractive forces between the apple and earth are the same in magnitude. But the corresponding acceleration of the apple is greater than the earth.

As you found in Part A, your weight will be greater than normal when the elevator is moving upward with increasing speed. For what other motion would your weight also be greater than your normal weight?

The elevator moves downward while slowing in speed.

You might think that it is never a good approximation to ignore air resistance. However often it is. Fire the cannonball without sure resistance and then fire it with air resistance. Then adjust the mass of the cannonball and see what happens to the trait. Don't change the diameter. When does the range with air resistance approach the range without air resistance

The range with air resistance approaches the range without air resistance as the mass of the cannonball is increased

Which requires more fuel: a rocket going from earth to the moon or a rocket returning from the moon to earth? Why?

The rocket leaving remarry to go to the moon will require more fuel bc earth had more mass than the moon. The embarrassing will exert bigger gravitational force to balance its weight leaving the earth than leaving the moon. Since the rocket will exert a larger force leaving the earth, it must do more work which takes more energy in the form of fuel

To begin your wingsuit flight you step off the edge of a high cliff. Why are you then momentarily weightless? At that point is gravity acting on you?

You are momentarily weightless bc you are momentarily between support forces which means you lose the supporting force for a moment. gravity is still acting on you

The following diagrams are the same as those from part A. This time rank the pairs from left to right based on size of the acceleration the asteroid on the left would have due to the gravitational force exerted on it by the object on the right from the largest to smallest

asteroid to Sun asteroid to Earth asteroid to Moon asteroid to asteroid asteroid to hydrogen atom

Consider a space pod somewhere between Earth and the Moon, at just the right distance so that the gravitational attractions to Earth and the Moon are equal. Is this location nearer Earth or the Moon?

nearer the Moon

The following diagrams are the same as those from Part A. Again considering only the two objects shown in each pair, this time rank the strength, from strongest to weakest, of the gravitational force acting on the object on the right.

sun earth moon asteroid hydrogen atom

The following five diagrams show pairs of astronomical objects that are all separated by the same distance d. Assume the asteroids are all identical and relatively small, just a few kilometers across. Considering only the two objects shown in each pair, rank the strength, from strongest to weakest, of the gravitational force acting on the asteroid on the left.

sun earth moon asteroid hydrogen atom

The range is the horizontal distance from the cannon when the pumpkin hits the ground. This distance is given by the product of the horizontal velocity and the amount of time the pumpkin is in the air. Set the initial speed to 14 m/s and fire the pumpkin several times while varying the angle between the cannon and the horizontal. For which angle is the range a maximum

45

In the previous part you discovered that the trajectory of an object does not depend on the objects size or mass. But if you have ever seen a parachutist or a feather falling you know this isn't really true. That is bc we have been neglecting air resistance and we will now study it's effects here. For the following parts select the lab mode of the simulation found at the bottom of the screen. Notice that can adjust the mass and diameter of the object being launched. Turn on air resistance by checking the bud. Fire a cannonball with an initial speed of 18 m/s and an angle of 45° compare the trajectory to the case without air resistance. How do the trajectories diffwr

The trajectory with air resistance has a shorter range