The radius of our galaxy is 3 × 10^20 m.
(a) Can a person, in principle, travel from the center to the edge of our galaxy in a normal lifetime? Explain, using either time-dilation or length-contraction arguments.
(b) What constant velocity would he need to make the trip in 30 years (proper time)?
for part a i get how to use the argument for time dilation but how would you argue for length contraction?2 AnswersPhysics6 months ago
One way to measure the speed of bullets with a ballistic pendulum (this is just a block
hanging from a rope or string that ‘absorbs’ the bullets) is to shoot a steady stream of
bullets into the pendulum, which will push it aside and hold it in a rough equilibrium
position at some angle. The speed can be calculated from this equilibrium angle. Suppose
that you shoot .22-caliber bullets of mass 15 g into a 4.0 kg ballistic pendulum at the rate of 2 per second. You find that the equilibrium angle is 24◦
. What is the speed of the
bullets?2 AnswersPhysics9 months ago
At a height of 1500m a dive bomber in a vertical dive at 300km/h shoots a canon at target on the ground. Relative to the bomber the initial speed of the projectile is 700m/s. what will be the impact speed of the projectile on the ground. How long will it take to get there. Ignore air friction and use the dive bomber as your frame of reference.
A boy and a girl are engaged in a tug-of-war. Suppose that they are evenly
matched, and neither moves. The boy pulls toward the left on the rope with a force of
250 N, and the girl pulls toward the right with a force of 250 N.
(a) Draw separate free-body diagrams for the boy, the girl, and the rope. In each
of these diagrams include all the appropriate horizontal forces (ignore the vertical
forces). (2 marks)
(b) What is the force that the ground exerts on the boy? On the girl? (2 marks)
(c) What is the tension in the rope? (2 marks)
(d) The girl ties her end of the rope to a stout tree and walks away, while the boy
continues pulling as before. What is the tension in the rope now?
a boat with maximum speed v (relative to the water) is on one shore of a river of width d. The river is flowing at speed V. Traveling in a straight line, how long does it take to get to a point directly opposite? What is the fastest crossing time to any point?
I feel like I’m wrong somewhere , I just need to know whether my idea makes sense or not , so we have the apparatus as :
Cylinder made of aluminum
We have two different stands , one for the tennis ball attached to a metal wire and the other for the cylinder
So my understanding was to:
1) find I (inertia) of the cylinder by I= 1/2*pi*(h1*R1^4+h2R2^4-h2R1^4) this formula was already given to me
2) find the period of oscillation of the cylinder using stopwatch (each oscillation is rotating I assume)
3) use w=2pi/t to find w and then use w^2= K/I to find K the torsional constant of the wire
Now this is where I get confused
To find the inertia of the tennis ball do it attach the tennis ball to the cylinder to find new period of oscillation and hence will find new w and k is constant so Inertia of the ball will be found using w^2 = k/I
Is this right? Also how would I attach the tennis ball to the cylinder ? Will appreciate any help4 AnswersPhysics10 months ago
The water in a river flows uniformly at a constant speed of 2.50m/s between two parallel banks 80.0m apart. You are to deliver a package directly across the river, but you can only swim at 1.5m/s. If you choose to minimize the distance downstream that the water carries you, in what direction should you head?3 AnswersPhysics10 months ago
light plane attains an airspeed of 500 km/h. The pilot sets out for a destination 800 km due north but discovers that the plane must be headed 20.0 degree East of due North to fly there directly. The plane arrives in 2.00 h. what were the (a) magnitude and (b) direction of the wind velociTy
I can’t seem to understand how to draw the diagram, if someone could draw out the diagram I would be grateful
In a flying ski jump, the skier acquires a speed of 110 km/h by racing down a steep hill and then lifts off into the air from a horizontal ramp. Beyond this ramp, the ground slopes downward at an angle of 45◦. (a) Assuming that the skier is in a free-fall motion after he leaves the ramp, at what distance down the slope will he land? What is his displacement vector from the point of ‘lift off’?2 AnswersPhysics11 months ago
work function of Se is 492.3 kJ/mol. If Selinium is irradiated with photon of
wavelength 200 nm, find the momentum of the photon and the ejected electron?2 AnswersPhysics11 months ago