Mechanics questions | form five Physics

An object of mass 2​ kg is attached to the hook of a spring balance which is suspended vertically to the roof of a lift. What is the reading on the spring balance when the lift is:

1. going up with the rate of 0.2​ ms^-2 ​
2. going down with an acceleration of 0.1​ms​^-2 ​
3. ascending with uniform velocity of 0.15​ ms ^-1

1. Define the term inertia.
2. Why is Newton’s first law of motion called the law of inertia?

A jet of water from a fire hose is capable of reaching a height of 20​m .​ If the cross sectional area of the hose outlet is 4.0×10​^-4​ m^2​ ​ , calculate the

1. Minimum speed of water from the hose.
2. Mass of water leaving the hose each second.
3. Force on the hose due to the water jet.

A boy ties a string around a stone of mass 0.15​ kg and then whirls it in a horizontal circle at constant speed. If the period of rotation of the stone is 0.4sec and the length between the stone and the boy’s hand is 0.50​ m ; ​

1. Calculate the tension in the string.
2. State one assumption taken to reach the answer in (i).

1. Define the term trajectory.
2. Briefly explain why the horizontal component of the initial velocity of a projectile always remains constant.

1. List down two limitations of projectile motion.
2. A body projected from the ground at the angle of 60° is required to pass just above the two vertical walls each of height 7m. If the velocity of projection is 100ms^​-1​ , calculate the distance between the two walls.

A fireman standing at a horizontal distance of 38m from the edge of the burning storey building aimed to raise streams of water at an angle of 60° into the first floor through an open window which is at 20m high from the ground level. If water strikes on this floor 2m away from the outer edge,

1. Sketch a diagram of the trajectory.
2. What speed will the water leave the nozzle of the fire hose?

1. Mention three effects of looping the loop.
2. Why there must be a force acting on a particle moving with uniform speed in a circular path? Write down an expression for its magnitude.

A driver negotiating a sharp bend usually tend to reduce the speed of the car.

1. What provides the centripetal force on the car?
2. Why is it necessary to reduce its speed?

A ball of mass 0.5​ kg is attached to the end of a cord whose length is 1.5​ m then whirled in horizontal circle. If the cord can withstand a maximum tension of 50​ N ​ , calculate the:

1. Maximum speed the ball can have before the cord breaks.
2. Tension in the cord if the ball speed is 5​m ​/ ​s ​ .