Explore BrainMass


Electric Current: Velocity of electron in a beam; Current of a beam

In a certain electron beam, there are 5.0 x 10^6 electrons per cubic centimeter. Suppose the kinetic energy of each electron is 10 keV and the beam is cylindrical with a diameter of 1 mm. (a) what is the velocity of an electron in the beam? (b) find the beam current.

S Inertial Frames

The following posting helps with problems involving inertial frames. See attached file for full problem description.

Determining Time Given Velocity: Ball Example

When a ball is thrown vertically upward, its height (h, in feet) above the ground after t seconds is described by the mathematical formula h = - 16t2 + 96t + 80. At what times is the ball 103 feet above the ground?

speed of boat in still water

Debbie traveled by boat 5 miles upstream to fish in her favorite spot. Because of the 4-mph current, it took her 20 minutes longer to get there than to return. How fast will her boat go in still water?

relative velocity and work done by the train

A train moves along the tracks at a constant speed u. A woman on the train throws a ball of mass m straight ahead with a speed v with respect to herself. a) What is the kinetic energy gain of the ball as measured by a person on the train? b) By a person standing by the railroad track? c) How much work is done by the woman

Average Velocity of a Particle

The position of a particle as a function of time is given by x(t) = (3.1 m/s)t - (4.2 m/s^2)t^2. What is the average velocity of the particle between t = 1.0 s and t = 2.0 s?

Magnitude of Average Velocity

A car moves from a point located 26.0 m from the origin and at an angle of 35.0 from the x-axis to a point located 56.0 m from the origin and at an angle of 60.0 from the x-axis in 2.50 s. What is the magnitude of the average velocity of the car? 12.7 m/s 13.7 m/s 16.1 m/s 18.3 m/s.

Speed of Baseball Player

A baseball player is running to second base at 5.63 m/s. When he is 5.20 m from the plate he goes into a slide. The coefficient of kinetic friction between the player and the ground is 0.220. What is his speed when he reaches the plate? 4.47 m/s 3.04 m/s 1.96 m/s He stops before reaching the plate.

Kinematics: How fast was the car going?

1) A policeman investigating an accident measures the skid marks left by a car. He determines that the distance between the point that the driver slammed on the brakes and the point where the car came to a stop was 34.0 m. From a reference manual he determines that the coefficient of kinetic friction between the tires and the ro

Value of angle x

A ball is thrown with a velocity of 40 m/s at an angle x above the horizontal. If the ball attains its maximum range, what was the value of the angle x?

Vertical Component of Velocity at Highest Point

A boy kicks a football with an initial velocity of 20 m/s at an angle of 30 degrees above the horizontal. What is the vertical component of its velocity at the highest point of its trajectory?

Horizontal component of velocity

A girl kicks a soccer ball with an initial velocity of 25 m/s at angle of 30 degrees above the horizontal. The horizontal component of the velocity of the ball is described by which of the following statements: It changes uniformly. It is zero. It is 25 m/s. It remains constant during the ball's flight.

Velocity and Acceleration for Travels

A car travels along east and its velocity decreases. The acceleration of the car is in which direction (northward, eastward, southward, or westward)? Explain.

Projectile Motion with a Baseball

A baseball thrown at an angle of 60 degrees above the horizontal strikes a building 20m away at a point 8m above the point from which it is thrown. Ignoring air resistance. Find A) the magnitude of the initial velocity of the baseball and B) the time it takes to reach the point.

Final velocity of baggage carrier

In problem 14.3(a), if the velocity of the 30 lb and 40 lb suit cases are 12 ft/s and 5 ft/s, respectively, when the first suit case of 30 lb was tossed into the carrier, the final velocity of the baggage carrier after the second baggage tossed into the carrier is: a. 4.25 ft/s b. 4.67 ft/s c. 3.87 ft/s d. 5.67 ft/s

Calculating The Acceleration And Velocity Of A Block

A block lies on a plane tilted at an angle theta = 22.0* to the horizontal, with the coefficient of kinetic friction mu_k = 0.17. a) Determine the acceleration of the block as it slides down the plane. b) If the block starts from rest 9.3 m up the plane from its base, what will be the block's speed when it reaches the bottom o

Cliff of the height calculation

A diver running 2.1 m/s dives out horizontally from the edge of a vertical cliff and reaches the water below 3.0s later. How high was the cliff and how far from its base did the diver hit the water?

Bullet's Projectile Motion

A gun fires a bullet at 250 m/s at a 45 degree angle with the horizontal. How far away from the point of launch will the bullet fall? And how much time will the bullet stay up in the air?

Spring and Simple Harmonic Motion

See attached file for full problem description. 1. Gina's favorite exercise equipment at the gym consists of various springs. In one exercise, she pulls a handle grip attached to the free end of a spring to 0.80 m from its unstrained position. The other end of the spring is held in place by the equipment frame. What is the magn

Newton's 2nd Law - Kinetics

Dynamics 12.8 A car has been traveling up along a 2 percent grade at a constant speed of 55 miles/hr. If the driver does not change the setting of the throttle or shift gears as the car reaches the top of the hill, what will be the acceleration of the car as it starts moving down the 3 percent grade? Dynamics 13.7 A 24-

Orbital Mechanics

A lunar landing craft needs to hover just above the surface of the moon, which has a gravitational acceleration of (1/6) g. The exhaust velocity is 2000m/s but fuel amounting to only 20% of the total mass can be used. How long can the landing craft hover?

Energy Questions

1) Find the curl, delta x F, for the following forces: (a) F = kr; (b) F = (Ax, By2, Cz3); (c) F = (Ay2, Bx, Cz), where A, B, C and k are constants. 2) Verify that the gravitational force - GMmr/r2 on a point mass m at r, due to a fixed point mass M at the origin, is conservative and calculate the corresponding potent

Rotationial kinematics

A basketball player is balancing a spinning basketball on the tip of his finger. The angular velocity of the ball slows down from 18.5 to 14.1 rad/s. During the slow-down, the angular displacement is 85.1 rad. What is the time it takes for the ball to slow down?

Rotational Kinematics of a Gymnast

A gymnast is performing a floor routine. In a tumbling run she spins through the air, increasing her angular velocity from 3.00 to 5.00 rev/s while rotating through one-half of a revolution. How much time does this maneuver take?

Calculations with Angular Velocity

A floor polisher has a rotating disk with a radius of 15 cm. The disk rotates at a constant angular velocity of 1.4 rev/s and is covered with a soft material that does the polishing. An operator holds the polisher in one place for 45s in order to buff an especially scuffed area of the floor. How far (in meters) does a spot on th

Radiological Physics Questions

1. Dennis Chapman did not eat for a few days and went to a restaurant which says buffet all you can eat just $4.95. Dennis was so happy that he started eating and eating till the owner of the restaurant asked Dennis "May I help you sir?". Dennis said yes, just go away and let me eat. After eating Dennis weight from 185 lb becam

Areal Velocity and Time Averages

Question: Show that the areal velocity is constant for a particle moving under the influence of an attractive force given by F(r) = -kr. Calculate the time averages of the kinetic and potential energies and compare the results of the viral theorem.

Falling Objects on the Earth and Moon

Imagine that you are sitting on top of a 10-meter tower and drop two objects: a $20 gold piece (weight = 33g, diameter = 34mm) and a silver dollar (weight =26.7 g, diameter = 38mm). 1. Which, if either, falls faster? How do you support your answer? 2. If you repeated the same experiment on the Moon, what would you notice?