Mechanics | Relativity Answers

A watermelon cannon fires a watermelon vertically up into the air at a velocity of +12.0 m/s, starting from an initial position 1.20 meters above the ground. When the watermelon reaches the peak of its flight, what is (a) its velocity, (b) its acceleration, (c) the elapsed time, and (d) its height above the ground?

The brochure advertising a sports car states that the car can be moving at 100.0 km/h, and stop in 37.19 meters. What is its average acceleration during a stop from that velocity? Express your answer in m/s2. Consider the car's initial velocity to be a positive quantity.

The driver of a jet-propelled car is hoping to break the world record for ground-based travel of 341 m/s. The car goes from rest to its top speed in 26.5 seconds, undergoing an average acceleration of 13.0 m/s2. Upon reaching the top speed, the driver immediately puts on the brakes, causing an average acceleration of −5.00 m/s2, until the car comes to a stop. (a) What is the car's top speed? (b) How long will the car be in motion?

A baseball is moving at a speed of 40.0 m/s toward a baseball player, who swings his bat at it. The ball stays in contact with the bat for 5.00×10−4 seconds, then moves in essentially the opposite direction at a speed of 45.0 m/s. What is the magnitude of the ball's average acceleration over the time of contact? (These figures are good estimates for a professional baseball pitcher and batter.)

In 1271, Marco Polo departed Venice and traveled to Kublai Khan's court near Beijing, approximately 7900 km away in a direction we will call positive. Assume that the Earth is flat (as some did at the time) and that the trip took him 4.0 years, with 365 days in a year. (a) What was his average velocity for the trip, in meters per second?

A jogger is moving at a constant velocity of +3.0 m/s directly towards a traffic light that is 100 meters away. If the traffic light is at the origin, x = 0 m, what is her position after running 20 seconds?

A clown is shot straight up out of a cannon. Determine the clown's vertical displacement from the instant he is shot out of the cannon at 0.0 seconds until when he reaches zero velocity at 2.5 seconds.

A jogger is moving at a constant velocity of +3.0 m/s directly towards a traffic light that is 100 meters away. If the traffic light is at the origin, x = 0 m, what is her position after running 20 seconds?

The shaft of diameter 200mm has to withstand an estimated axial thrust (compressive load) of 520kN and a torque of 150kN during normal operation.

Estimate the magnitudes of direct and shear stresses acting at a point on the surface of the shaft and indicate these stresses in a representative element.

In the spin cycle of a washing machine, the tub of radius 0.44 m rotates at a constant rate
of 705 rev/min. What is the maximum linear speed of the water inside the machine?
Answer in units of m/s.