Newton's first law and projectiles questions

Click For Summary
The discussion revolves around understanding Newton's first law and projectile motion through two question sets. In the first set, Mia Edwards' running scenario highlights the concepts of inertia, acceleration, and velocity, with a focus on calculating her maximum speed and whether she can break the 200-meter world record. The second set involves Luke, an archer, analyzing the trajectory of an arrow shot at a specific angle and speed, emphasizing the importance of sine and cosine in determining vertical and horizontal components of motion. Key points include the relationship between acceleration and velocity, the effect of gravity on projectile motion, and the need for calculations to determine flight time and target accuracy. Overall, the discussion seeks clarity on applying physics principles to these scenarios.
emma934
Messages
3
Reaction score
0
I just don't get these questions...please help.
() are what I think the answers are but I am not positive.
Question set 1:
Beginning from rest, Mia Edwards runs the 200 meter dash with an acceleration of 0.9 m/s2.
1. define inertia. (inertia- the tendency of an object to resist change)
2. what happens to Mia's velocity if acceleration is non-zero and in the same direction as her velocity? (if her acceleration is non-zero and in the same direction as her velocity than her velocity will increase.)
3. what is the highest velocity Mia reaches after 5 seconds? (4.5 m/s2)
4. the world record for the 200 meter race is 21.34 seconds. does she break the world record?
5. what would be the break down? acceleration second by second?
Question set 2:
Luke is an archer in the war. Using a bowl, he fires an arrow at 100 feet per second (fps) at 55 degrees above the horizontal ground.
1. what parts of a triangle are used for sine? what parts of a triangle are used for cosine? (to calculate sine on a triangle you divided the opposite by the hypotenuse. Cosine is calculated with the adjacent divided by the hypotenuse.
2. what should happen to arrow's vertical velocity as it comes down if gravity works in the same direction? (it gravity works in the same direction as the arrows then the vertical velocity of the arrow will increase.)
3. How long is the arrow in the air for in total?
4. Luke’s target is 613 feet away. Will he hit it?
 
Physics news on Phys.org
emma934 said:
I just don't get these questions...please help.
() are what I think the answers are but I am not positive.
Question set 1:
Beginning from rest, Mia Edwards runs the 200 meter dash with an acceleration of 0.9 m/s2.
1. define inertia. (inertia- the tendency of an object to resist change)
2. what happens to Mia's velocity if acceleration is non-zero and in the same direction as her velocity? (if her acceleration is non-zero and in the same direction as her velocity than her velocity will increase.)
3. what is the highest velocity Mia reaches after 5 seconds? (4.5 m/s2)
4. the world record for the 200 meter race is 21.34 seconds. does she break the world record?
i.e. how long would it take mia to run 200m given the information so far?

5. what would be the break down? acceleration second by second?
... well, what happens to the acceleration?

Question set 2:
Luke is an archer in the war. Using a bowl, he fires an arrow at 100 feet per second (fps) at 55 degrees above the horizontal ground.
Presumably Luke uses a bow, not a bowl?

1. what parts of a triangle are used for sine? what parts of a triangle are used for cosine? (to calculate sine on a triangle you divided the opposite by the hypotenuse. Cosine is calculated with the adjacent divided by the hypotenuse.
2. what should happen to arrow's vertical velocity as it comes down if gravity works in the same direction? (it gravity works in the same direction as the arrows then the vertical velocity of the arrow will increase.)
3. How long is the arrow in the air for in total?
Time to go from the ground, to it's highest point, back to the ground again?
The speed when it hits the ground is the same as the initial speed.
You need to divide the motion into horizontal and vertical components to work this out.

4. Luke’s target is 613 feet away. Will he hit it?
... you need to do (3) first. What is the horizontal acceleration?
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

Similar threads

Replies
6
Views
2K
Replies
40
Views
2K
Replies
18
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
4
Views
4K
  • · Replies 35 ·
2
Replies
35
Views
4K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
10
Views
2K