Physics Answers

Arlene is stationary relative to the ground. Aiza is riding toward A rlene on her e-bike 5 m/s relative to the ground. Aiza throws a water balloon forward at 3 m/s relative to the e-bike. With what speed does it strike Arlene?

Joana Marie is a swimmer. She swims directly across a river flowing at 4 m/s with a velocity of 2 m/s. What will be the actual velocity of Joana Marie relative to the river? Determine its angle.(solution)

A manufacturer wishes to fabricate a step index optical fibre from a material such that relative core-cladding index difference is 0.01. The refractive index of cladding is 1.3. In other case, keeping the material of the core same, the cladding material is replaced by another medium, such that core-cladding index difference is now 0.02. Calculate the ratio of light gathering ability of the optical fibre for the two cases with refractive index of outer medium to be 1. Compare the two cables for their applications in communication. Suggest the measures to be done if graded index fibre is to be fabricated in both the cases and how it is going to change the properties and applications of cable.

Consider a wire of area A = 1m² initially far from any sources of magnetic field. A strong bar magnet with B = 1T near its poles is suddenly inserted into the loop, filling the loop completely. If the time required to insert the magnet is t = 0.1s , what is the approximate value of the induced emf in the loop?

1. 200-gram ball, m1 and a 100-gram ball, m2, connected by a rod with length of 60 cm. The axis of rotation is located at ball m2. What is the moment of inertia of the balls. Ignore rod’s mass
2. A slim rod 2.0 m long has two small 0.50-kg bodies attached at its two ends and a 0.25-kg body at its midpoint as shown. Find the moment of inertia about an axis perpendicular to the rod has negligible mass.
3. Four identical masses of 2.0 kg each situated at the four corners of a square. A side of the square measures 3.0 m. Find the moment of inertia about an axis passing through the center of the square and perpendicular to its plane. 

1. A wheel with a diameter of 80cm speeds up from 30 rad/s to 80 rad/s. The linear acceleration at the edge of the wheel is 15 m/s2. How many revolutions will the wheel go through during this period?

A disk with diameter of 60 cm speeds up from 20 rad/s to 40 rad/s in 5 seconds. (a) How many revolutions will the disk go through during that time period? (b) What is the average angular acceleration of the disk? (c) What is the average linear acceleration of the disk?

A small stone is thrown away into the air with a velocity of 15 m/s at an angle of 30 degree along the horizontal. (With solution)

a. Find the maximum height reached by the object,

b. Time of flight, and

C. Range

The door of a five star hotel consists of four rectangular glass panels measuring 1.0 m by 2.5 m equally mounted on a rotating rod.Find the moment of inertia of the door with respect to this rod.Consider the dimensions of the rod as negligible compared to the dimensions of the glass panel.

Nikki drops her doll from the rooftop 10 m above the ground. Neglecting air resistance, how long it will take to reach the ground?