# relative motion

1. ### 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. ### 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. ### 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. ### 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. ### 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...

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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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...