Physics Answers

Someone goes skiing. He starts from rest at the top of a ski hill with an incline of 22 degrees up from the ground. If this person is going 26 m/s after 10 seconds, what is the coefficient of friction between his skis and the hill?

One kilogram of water at 5˚C is heated to 100˚C. Compute its change in entropy. Assume that the specific heat of water is constant at 4190 J/kg·K over this temperature range

If you can do the same amount of work over a shorter period compared to your classmate, in physics, are more powerful?

A. No, because you accomplished the same amount of work.

B. No, because power is concerned with force, not time.

C. Yes, because you accomplished the same amount of work in a small

period.

D. Yes, because power is relative and having yourself as a reference

frame makes you more powerful.

A weightlifter holds a 100kg barbell stationary in the air. While they are

holding up the barbell, what is the value of the work they are exerting?

A. Positive C. Zero / No value

B. Negative D. Can’t be determined

A hydraulic press has a small piston of diameter =3.4 cm and the large piston of diameter=30 cm. If the force applied to the small piston (F1) is 395 N.

What is the mass of the car that can be raised at the large piston (in kg)?

The gravitational force exerted on a solid object is 113 N. when the object is suspended from a spring scale and submerged in water (Density of water=1000 kg/m3), the scale reads 50 N. The density of this object (in kg/m3) is:

Discuss, giving examples, the significance of the bonding energy (E0).

Given that the potential energy of a pair of atoms in a solid is raised by 1 eV when their

separation is changed by 1Å, calculate the macroscopic elastic modulus of the lattice.

The total potential energy of a system of two atoms is given by

U=-p/r³+q/r^6

The atoms form a stable bond at a bond length of 3.2 Å with the release of 12 eV.

a) Calculate p and q.

b) Determine the critical distance.

• At critical separation, force is maximum

c) Find the force needed to dissociate this molecule.

At a point 10^2m from a positive point charge q, the field strength of an electric Field is 14400vm^-1 and the potential is 144v. Find the magnitude of q and the potential at a point 2cm from the charge.