Mechanics | Relativity Answers

A spring with a mass of 4 kg has natural length 0.5 m. A force of 25.6 N is required to maintain it stretched to a length of 0.7 m. If the spring is stretched to a length of 0.7 m and then released with initial velocity 0, find the position of the mass at any time.

a bird is flying due east.its distance from a tall building is givin by x(t)=28m + (12.4 m/s)t - (0.0450 m/s^3)t^3.what is the instantaneous velocity of the bird when t=8s ?

A car of mass 100 kg moving on a horizontal road with a steady velocity of 10 m/s has a total frictional on it of 400N. Find the power due to the engine.

A car now climbs a hill an angle of 8° to the horizontal. Assuming frictional force stays same what engine power is needed to keep the car moving at Km s−1.

A particle is projected with speed V at an angel ∝ to the horizontal. Find the speed of the particle when it is at a height h.

A simple pendulum consisting of a small heavy bob attached to a light string of length 40cm is released from rest with the string at 60° to the downward vertical. Find the speed of the pendulum bob as it passes through its lowest point.

(6.1 UP 11e). You push your physics book 1.5 meters along a horizontal table top with a horizontal force of 2.40N. The opposing force of friction is 0.60N.
a) How much work does your 2.40N force do on the book?
b) What is the work done on the book by the friction force?
c) What is the total work done on the book?

(6.11 UP 11e). The dinosaur Tyrannosaurus rex is thought to haeve had a mass of about 7000kg.
a) treat the dinosaur as a particle and estimate its kinetic energy at a walking speed of 4.0 km/h
b) with what speed would a 70 kg person have to move to have the same kinetic energy as a walking T-rex?

does accelaration inversely proportional to inertia

A tennis player wishes to return the ball so it just passes over the top of
the net at a point where the net is 1.0 m high. He can return the ball at a
speed of 14 ms-1
from a position that is 0.4 m vertically below the top of
the net and is 8.0 m from the point where he intends the ball to cross the
net.
a. At what angles to the horizontal could the player strike the ball in
order to do this?

A tennis player wishes to return the ball so it just passes over the top of
the net at a point where the net is 1.0 m high. He can return the ball at a
speed of 14 ms-1
from a position that is 0.4 m vertically below the top of
the net and is 8.0 m from the point where he intends the ball to cross the
net.
a. At what angles to the horizontal could the player strike the ball in
order to do this?
b. In each case what will be the total horizontal distance travelled by
the ball before it strikes the ground on the other side of the net?
c. Without further calculation, sketch the trajectories in each case.