Need help with 2 Kinematics questions (New to forum and physics)

In summary, the conversation is about the last two homework questions in physics. The first question involves creating a triangle and solving for the hypotenuse, while the second question involves using the equation for position/displacement and converting units to determine the time it takes for light to travel from a spacecraft to Earth. The given equations are ⃗v = ∆⃗x ∆t, ⃗x = ⃗x 0 + ⃗v t, ⃗a = ∆⃗v ∆t, ⃗v = ⃗v 0 + ⃗a t, and v 2 = v 20 + 2 a ( x − x 0
  • #1
shivam28
5
0
Homework Statement
1. Two aircraft depart simultaneously from the same location along perpendicular trajectories, with constant speeds equal to 300 km/h and 250 km/h, respectively. The two aircraft can communicate directly with each other only if they are less than 10 km apart. How long after departure will the two aircraft be out of communications range?

2. The New Horizons spacecraft was launched by NASA to study the dwarf planet Pluto in January of 2006. In July, 2015, the spaceship arrived at Pluto’s vicinity and sent back pictures of its surface. The estimated distance between Earth and the craft, at its closest approach point to Pluto, was 32 au (astronomical unit; 1 au = 1.50 × 108 km). Considering that the speed of light is 3.0 × 105 km/s, the image received by Earth observatories traveled, from New Horizons to Earth, during approximately:

A. 0.1μs
B. 1h
C. 4.5h
D. 2d
E. 0s
Relevant Equations
⃗v = ∆⃗x ∆t
⃗x = ⃗x 0 + ⃗v t

⃗a = ∆⃗v ∆t
⃗v = ⃗v 0 + ⃗a t
v 2 = v 20 + 2 a ( x − x 0 )
⃗x = ⃗x + v⃗ t + 1 ⃗a t 2
I am new to physics and these are my last two questions of my homework. I am extremely confused on what to do but I do know that for question 1 I need to create a triangle and solve for the hypotenuse, and for question 2 I believe I need to input my given values into the equation for position/displacement: ⃗x = ⃗x + v⃗ t + 1 ⃗a t 2. However once again, I am extremely confused.
 
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  • #2
shivam28 said:
Homework Statement: 1. Two aircraft depart simultaneously from the same location along perpendicular trajectories, with constant speeds equal to 300 km/h and 250 km/h, respectively. The two aircraft can communicate directly with each other only if they are less than 10 km apart. How long after departure will the two aircraft be out of communications range?

2. The New Horizons spacecraft was launched by NASA to study the dwarf planet Pluto in January of 2006. In July, 2015, the spaceship arrived at Pluto’s vicinity and sent back pictures of its surface. The estimated distance between Earth and the craft, at its closest approach point to Pluto, was 32 au (astronomical unit; 1 au = 1.50 × 108 km). Considering that the speed of light is 3.0 × 105 km/s, the image received by Earth observatories traveled, from New Horizons to Earth, during approximately:

A. 0.1μs
B. 1h
C. 4.5h
D. 2d
E. 0s
Homework Equations: ⃗v = ∆⃗x ∆t
⃗x = ⃗x 0 + ⃗v t

⃗a = ∆⃗v ∆t
⃗v = ⃗v 0 + ⃗a t
v 2 = v 20 + 2 a ( x − x 0 )
⃗x = ⃗x + v⃗ t + 1 ⃗a t 2

I am new to physics and these are my last two questions of my homework. I am extremely confused on what to do but I do know that for question 1 I need to create a triangle and solve for the hypotenuse, and for question 2 I believe I need to input my given values into the equation for position/displacement: ⃗x = ⃗x + v⃗ t + 1 ⃗a t 2. However once again, I am extremely confused.

Let's see what you can do about the hypoteneuse in question 1. You don't seem so confused about that.
 
  • #3
Hints for Problem #2:
It is given that the spacecraft traveled a distance of 32 au (the distance between Earth and its closest approach point to Pluto). The first thing we need to do is convert 32 au into kilometers, since the speed of light is given in units of km/s.
##32 \text{ au} = 1.50 \times 10^8 \text{ km}##
##(1.50 x 10^8)(32) = 4.80 \times 10^9 \text{ km}##

The question asks for the time it takes for light to travel from the spacecraft back to Earth at ##3.8 \times 10^5 \text{ km/s}##.
So, we already know that the distance is:
##Δx=4.80 \times 10^9 \text{ km}##
And it's given that:
##v=3.8 \times 10^5 \text{ km/s}##

So, all you need to do now is solve for t.
 
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FAQ: Need help with 2 Kinematics questions (New to forum and physics)

1. What is kinematics?

Kinematics is a branch of physics that deals with the study of motion, without considering the causes of motion. It involves analyzing the position, velocity, and acceleration of an object in order to describe and predict its motion.

2. What is the difference between speed and velocity?

Speed is a measure of how fast an object is moving, while velocity is a measure of both the speed and direction of an object's motion. In other words, velocity includes both the magnitude and direction of an object's speed.

3. How do you calculate acceleration?

Acceleration is calculated by dividing the change in velocity by the change in time. The formula for acceleration is: a = (Vf - Vi) / t, where a is acceleration, Vf is final velocity, Vi is initial velocity, and t is time.

4. What is the difference between average and instantaneous acceleration?

Average acceleration is the change in velocity over a certain period of time, while instantaneous acceleration is the acceleration at a specific moment in time. In other words, average acceleration is an overall measure, while instantaneous acceleration is a specific value at a specific time.

5. How can you use kinematics equations to solve problems?

Kinematics equations can be used to solve problems involving motion by plugging in known values for variables such as time, velocity, and acceleration. These equations allow you to calculate unknown variables and make predictions about an object's motion.

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