relative motion

  1. Like Tony Stark

    Find the angle so that it seems that Mars is approaching to you

    I know that ##v_{M/S}=v_M - v_S##. I also know that ##v_M = (-24.1;0)##. Then, using some trigonometry, ##v_S=(-19.3 sin 30°;19.3 cos 30°)##. So I can find ##v_{M/S}##. But that doesn't tell me anything about the angle ##\beta##.
  2. Like Tony Stark

    Body connected to two parts of a rope on an inclined plane

    The thing is that my professor said that if the velocity of ##A## is ##400 cm/s##, the velocity of ##B## is ##200 cm/s## because "##B## is connected to two parts of the rope and ##A## is conected just to one part", and he also said that that ##200 cm/s## is the velocity of ##B## with respect to...
  3. Like Tony Stark

    Find the force needed for a body on an inclined plane to be static?

    Here, I have two doubts 1) if the surfaces are frictionless, then there's no force being applied on the ##x' axis## of ##m_1## except from the weight, so it should be sliding, shouldn't it? So, there's no force that I could apply to ##m_2## to keep ##m_1## in equilibrium since any force that I...
  4. Like Tony Stark

    Measuring position, velocity and acceleration in relative motion

    Well, ##r(t)## in ##A## is just a vector ##(0;y)## because is tangent to the trajectory. Then, from the perspective of ##B## the particle moves in an uniform circular motion. Is this right? The velocity from ##B## must be ##\omega##, right? And what about acceleration?
  5. Like Tony Stark

    Particle moving in a rotating disc

    Well, I tried plugging the data in the formula. I know that ##\vec a_b = 0; \vec \omega=3 rad/s ; \vec r## can be calculated using trigonometry. Then I also know that ##v_{relx}= 10 cm/s##, ##a_{relx}=15 cm/s^2##, ##\vec {\dot{\omega}}=-10 rad/s^2##. But how do I get ##v_{rely}## and...
  6. Like Tony Stark

    Relative rotational motion on a disc

    The first doubt that comes to my mind is "I have to determine the acceleration with respect to what?", because the problem doesn't tell. Then, I have some problems when having to plug the data in the formula of acceleration. ##\vec a_B=0## because the origin isn't accelerated, ##\vec{\dot...
  7. Santilopez10

    Relative motion between cars with different types of movements

    I think my approach is quite wrong, still I gave it a shot: First I know that ##v_A=13.3 m/s=r\omega=60\omega \rightarrow \omega=0.2 \frac{rad}{s}## Then $$\vec a_A=-r\omega^2 e_r=-2.4 e_r$$ But ##e_r=\cos{\theta}i+\sin{\theta}j## and substituing the latter in the acceleration equation I have...
  8. Alexanddros81

    Determine the ground speed and the course of the plane

    1. Homework Statement 15.1 The airspeed of the plane is 200m/s, directed north. If the wind speed is 30m/s in the direction shown, determine the ground speed and the course (angle θ) of the plane. 2. Homework Equations 3. The Attempt at a Solution Is it so far correct the above? More...
  9. H

    Problem using vectors and relative motion

    1. Homework Statement A river of width 4 km flows at 5 km/h. A swimmer whose speed relative to water is 4 km/h, starts swimming from a point A on a bank. What minimum distance will the swimmer have to walk on the other bank to reach point B directly opposite to A? 2. Homework Equations Vba...
  10. Captain Levi

    Need help with Relative motion

    1. Homework Statement If a river is going 6 km/hr relative to the ground, a boat is going 14 km/hr relative to the river, and a man is jumping from one end of the boat to the other at 6 km/hr relative to the river. What is the speed of the man relative to the ground? I'm stuck between the...
  11. P

    Kinematics -- flying a plane in the wind to a destination

    1. Homework Statement A plane is taking off from an airport directly west of the airport it wishes to touch down in. The plane in still air can travel with a constant speed of 730 km/h. If a wind is blowing constantly at 92 km/h [45° S of E], at what angle must the plane fly to compensate for...
  12. M

    What is the angle and displacement of the plane?

    1. Homework Statement In the figure below, a radar station detects an airplane approaching directly from the east. At first observation, the range to the plane is d1 = 412 m at 40° above the horizon. The airplane is tracked for another 123° in the vertical east–west plane, the range at final...
  13. R

    Relative motion of two observers

    1. Homework Statement Two observers having identical instruments carry out identical experiments to study the motion of a massive particle. First observer concludes that the particle is moving in a straight line with constant velocity while the second observer concludes that the particle is...
  14. L

    I Derivation of Rocket Equation Using Relative Velocity

    Based on my current understanding of the problem I do not see this following derivation as valid, although this is what was given in my course notes. Although this particular example is from an undergraduate physics course this is not a homework problem: I'm confused about the underlying...
  15. T

    Airplane and Relative motion

    1. Homework Statement After flying for 15 min in a wind blowing 42 km/h at an angle of 31° south of east, an airplane pilot is over a town that is 50 km due north of the starting point. What is the speed of the airplane relative to the air? 2. Homework Equations Vx of wind=42km/hr*cos(31) Vy...
  16. A

    Minimum distance between bomb and shell

    1. Prolem Statement:- An aircraft is flying horizontally with constant velocity = ##200 m/s##, at a height = ##1 km## above the ground. At the moment shown, a bomb is released from aircraft and the canon- gun below fires a shell with initial speed = ##200 m/s##, at some angle #\theta#. 1)For...
  17. A

    Why can't the acceleration of a wedge be found by simply...

    ↪ mentor note: thread moved to h/w forum so template is missing ↩ Hi, I have recently been learning relative acceleration and I have a bit of trouble with basics; In a problem with a smooth wedge on a smooth plane, a mass is gently placed on the wedge and I've been asked to find the...
  18. A

    Sphere rolling with slipping on a movable platform

    1. Homework Statement A sphere (of radius r and mass m) rotating with angular velocity ω0 is lowered onto the edge of a floating platform of length L and mass M. The platform can move freely on water. The platform is rough and the sphere rolls all the way from one edge to the other edge of the...
  19. S

    Relative motion and conservation of momentum

    1. Homework Statement A 52kg man is on a ladder hanging from a balloon that has a total mass of 450kg (including the basket passenger). The balloon is initially stationary relative to the ground. If the man on the ladder begins to climb at 1.2m/s relative to the ladder, (a) in what direction...
  20. hackhard

    B How to check if frame is inertial?

    inertial frame is one in which isolated particle has constant velocity but is there actually any "isolated particle " ? how then can frame be defined as or not being inertial ? or is it that - for a system in which acceleration due to external forces is equal for all members , the frame of...
  21. D

    Relative Motion With Vectors

    1. Homework Statement A ball rolls with a velocity of 14 mm/s [W] on a board that is being pulled [E 60o N] at 20.0 mm/s. What is the velocity of the ball relative to the floor? b = ball x = board f = floor 2. Homework Equations V_bf = V_bx + V_xf 3. The Attempt at a Solution I tried to...
  22. clydefrog

    Plane ride relative motion problem

    1. Homework Statement You are traveling on an airplane. The velocity of the plane with respect to the air is 160 m/s due east. The velocity of the air with respect to the ground is 41 m/s at an angle of 30° west of due north. 1) What is the speed of the plane with respect to the ground? 2...
  23. C

    Minimum distance to avoid collision using relative motion

    1. Homework Statement 2 cars with velocities 10 m/s and 20 m/s are travelling in opposite directions, having uniform retardation of 2m/s^2 and 1m/s^2 respectively. Find minimum separation between them such that they don't collide. 2. Homework Equations $$v^2=u^2 + 2as$$...
  24. L

    Inelastic collision of plane onto a barge? (challenging)

    1. Homework Statement A 1000 kg plane is trying to land on the deck of a 2000 kg barge at rest on the surface of the sea. The only frictional force to consider is between the plane’s wheels and the deck, and this braking force is constant and equal to one-quarter of the plane’s weight. What...
  25. T

    Relative angular velocity in a rotating rod

    Consider a rod AB rotating about one of it's end A with angular velocity w. Now angular velocity of each point of the rod is same i.e. w. But if we have to find the relative angular velocity of the end B w.r.t. mid point of rod, what it will be? Will it be zero because, w-w=0 or first we...
  26. R

    Physics homework help? Grand Canyon problem

    1. Homework Statement If you were to throw a large log over the edge of the Grand Canyon and it took 5.65 seconds to hit the ground, calculate the velocity of the log at impact in m/s and calculate the distance the log fell in feet. 2. Homework Equations vf=vi + at, s=d/t 3. The Attempt at...
  27. R

    Relative Motion Homework Problem?

    1. Homework Statement "To illustrate this principle, consider a plane flying amidst a tailwind. A tailwind is merely a wind that approaches the plane from behind, thus increasing its resulting velocity. If the plane is traveling at a velocity of 100 km/hr with respect to the air, and if the...
  28. R

    Relative Motion problem

    1. What is the velocity of John relative the bus in each of the following situations: A) John is sitting on the street and the bus is moving at 30m/s toward him B)John is sitting in his car traveling North at 25m/s toward a stationary bus? C)John is sitting in his car traveling North at 35 m/s...
  29. R

    Relative Motion/Velocity?

    A police car is chasing a stolen car ahead of it. If the police car is traveling at 150 km/h (N) and the stolen car is traveling at 120 km/h (N), then determine: a) velocity of police car relative to ground b) vel. to the pol. car relative to the stol. car c) vel of stol car relative to the pol...
  30. 2

    Deriving the doppler shift equation for sound

    I am looking at derivations of the Doppler effect for sound and light, and I am very confused about what stays the same when it comes to sound. In this video, at 5:10, it is said that the wavelength will be the same. I'm not sure I agree with this because I'm pretty sure both the observed...
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