Mechanics | Relativity Answers

a bus running at a speed 18 km/hr is stopped in 2.5 seconds by applying breaks calculate the retardation produced.

A rocket is fired in deep space, where gravity is negligible. In the first second it ejects 1 160 {\frac{1}{160}} of its mass as exhaust gas and has an acceleration of 15.0m/s 2 m/s^2 .
1)What is the speed of the exhaust gas relative to the rocket?

Pluto's diameter is approximately 2370 km {\rm km}, and the diameter of its satellite Charon is 1250 km {\rm km}. Although the distance varies, they are often about 1.91×104km km apart, centre-to-centre.
1)Assuming that both Pluto and Charon have the same composition and hence the same average density, find the location of the centre of mass of this system relative to the centre of Pluto.

An astronaut in space cannot use a scale or balance to weigh objects because there is no gravity. But she does have devices to measure distance and time accurately. She knows her own mass is 76.4kg kg , but she is unsure of the mass of a large gas canister in the airless rocket. When this canister is approaching her at 3.50m/s m/s , she pushes against it, which slows it down to 1.10m/s m/s (but does not reverse it) and gives her a speed of 2.40m/s m/s .
1)What is the mass of this canister?

A 2.00kg kg stone is sliding to the right on a frictionless horizontal surface at 5.50m/s m/s when it is suddenly struck by an object that exerts a large horizontal force on it for a short period of time.
1)What impulse does this force exert on the stone?
2)Just after the force stops acting, find the magnitude of the stone's velocity if the force acts to the right.
3)Just after the force stops acting, find the magnitude of the stone's velocity if the force acts to the left.

A 0.160-kg {\rm kg} hockey puck is moving on an icy, frictionless, horizontal surface. At t=0 t=0 the puck is moving to the right at 2.91m/s m/s .
1)Calculate the magnitude of the velocity of the puck after a force of 25.9N N directed to the right has been applied for 6.0×10−2s s .
2)If instead, a force of 12.7N N directed to the left is applied from t=0 t=0 to t= t= 6.0×10−2s s , what is the magnitude of the final velocity of the puck?

A 115kg kg mail bag hangs by a vertical rope 3.6m m long. A postal worker then displaces the bag to a position 2.1m m sideways from its original position, always keeping the rope taut.
1)What horizontal force is necessary to hold the bag in the new position?
2)As the bag is moved to this position, how much work is done by the rope?
3)As the bag is moved to this position, how much work is done by the worker?

A car accelerates uniformly from standstill to 60 mi/hr in 4s. What is its acceleration? How far does it travel during this time interval?

if no force acting acting on a body,it

Ratio of the ranges of the bullets fired from a gun at angle θ, 2θ and 4θ is found in the ratio x : 2 : 2, then the value of x will be (Assume same speed of bullets)
A) 1
B) 2
C)√3
D) none of these.