Mechanics | Relativity Answers

The 200g mass is replaced with 100g mass. What is the new length of the spring?

A ship is travelling due east at 30 km/hr and a boy runs across a deck in a south west direction at 10 km/hr. find the velocity of the boy relative to sea

a bus is moving along a road at the rate of 2 m/s. In what direction should a stone be projected from it with a velocity of 12 m/s so that the resultant motion of the stone may be right angle to the motion of the bus ?

5. The force (not the power) required to tow a boat at constant velocity is proportional to the speed. If a speed of 4.0 km/h requires 7.5 kW power, how much power does a speed of 12 km/h require?

3. A rock is dropped (from rest) from the top of a 60 m tall building. How far above the ground is the rock 1.2 s before it reaches the ground?
4. A mother racing her son has half the kinetic energy of the son, who has half the mass as the mother. Mother speeds up by 1.0 m/s and then has the same kinetic energy as that of the son. What are the original speeds of the mother and the son?

1. Water drips from the nozzle of a shower onto the floor 200 cm below. The drops fall at regular (equal) intervals of time, the first drop striking the floor at the instant the fourth drop begins to fall. Find the locations of the second and third drops when the first strikes the floor.
2. A parachutist bails out and freely falls 50 m. Then the parachute opens and thereafter she decelerates at 2.0 m/s2. She reaches the ground with a speed of 3.0 m/s. How long is the parachutist in the air? At what height does the fall begin?

11. A stone is dropped from the top of a tall building. Two second later another stone is dropped from the same point. Calculate the distance between the stones, 2.5 second after the 2nd stone was dropped. Ignore air resistance. Express your answer in meter.

13. A person performs the following experiment to measure the acceleration of an elevator. He takes a weighing machine, keeps it on the floor of an elevator. He records his mass as 50 kg when the elevator is at rest. He continues to stand on the machine and then starts the elevator, which begins to move down. He records his mass to be 48 kg during the downward acceleration of the elevator. From this observation, calculate the acceleration of the elevato

Police investigators, examining the scene of an accident involving two cars, measure the 72m long skid marks of one of the cars with a mass of 2500kg. The coefficient of kinetic friction between rubber and pavement is about 0.80. Estimate the initial speed in mph of that car assuming a level road.

A piledriver hammer of mass 150 kg falls freely through a distance of 5 m to strike a pile of mass 400 kg and drives it 75 mm into the ground. The hammer does not rebound when driving the pile. Determine the average resistance of the ground.

Compare and contrast the use of D’Alembert’s principle with the principle of conservation of energy when solving the problem