constant acceleration

"A runner hopes to complete the 10,000-m run in less than 30.0 minutes. After exactly 27.0 minutes, there are still 1100 m to go. The runner must then accelerate at 0.20 m/s^2 for how many seconds in order to achieve the desired time?" Here's what I've done: So far, the runner has gone 8900 m in 1620 s, which should give h ...continues

Rotational Kinematics

A solid sphere of uniform density starts from rest and rolls without slipping a distance of d = 4.2 m down a q = 23° incline. The sphere has a mass M = 4.1 kg and a radius R = 0.28 m. a) Of the total kinetic energy of the sphere, what fraction is translational? b) What is the translational kinetic energy of the sphere when i ...continues

constant acceleration

"A helicopter is ascending vertically with a speed of 5.50 m/s. At the height of 105 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground?" Here's what I've done: X(0) = 0 (where package is dropped from) X = 105 m V(0) = 5.5 m/s V = ? a = -9.8 m/s^2 (nega ...continues

Rotational Kinematics

A man of mass mm = 95 kg decides to paint his house. To do this, he builds a platform using a uniform beam with a mass of mb = 100 kg and a length of L = 7 meters. The beam is supported by two sawhorses, as shown in the diagram above. (a) If the man stands over the support at point B, calculate the force exerted by the beam on ...continues

Newton's word problem

Jane, whose mass is 50.0kg, needs to swing accross a river(having width of D) filled with man-eating crocodiles to save Taezan from danger. She must swing into a wind exerting a constant horizontal force F on a vine having a length L and initially making an angle (theta) with the vertical. Taking D=50.0m F=110 N L=40.0m and ...continues

Newton's word prob

m2= 3.00kg, m1 = 5.00kg. h=4 Two objects are connected by a light string passing over a light frictionless pulley . The object of 5.00kg mass is released from rest. Using the principle of conservation of energy. (a) determine the speed of 3.00kg object just as the 5.00kg object hits the ground. (b) find the maximum height ...continues

constructing a corbeled arch using 0.3 meter long brinks

Four bricks are to be stacked at the edge of a table, each brick overhanging the one below it, so that the top brick extends as far as possible beyond the edge of the table. (a) To achieve this, show that successive bricks must extend no more than (starting at the top brick)1/2, 1/4, 1/6, and 1/8 of their length beyond the one b ...continues

Physics word problem

Using the principle of conservation of energy. (a) determine the speed of 3.00kg object just as the 5.00kg object hits the ground. (b) find the maximum height to which the 3kg object rises. (c) How will this mass as it descends rise the mass up as v=0 (m1 and m2 both have a v=0) (solve for y) I have the answers to (a) 4.43m/s (b ...continues

Rotational Kinematics

A 15 kg uniform disk of radius R = 0.25 m has a string wrapped around it, and a m = 5 kg weight is hanging on the string. The system of the weight and disk are initially at rest. When the 5 kg weight is released, it moves down and the disk rotates. Consider the point when the 5 kg weight is moving with a speed of 1.3 m/s. a) W ...continues

mechanics question on gravity

Q1. a stone of mass 80 grams is released from rest at the top of a vertical cliff. after falling for 3 seconds, it reaches the ground and penetrates 9 cm into the ground. calculate 1. the height of the cliff 2. the average force resisting the penetration (assume gravitational acceleration g=10m/sec2)