Physics Answers

Consider the following:

If two equal mass objects have the same net force acting on them, then they will be experiencing the same change in speed.

(a) Is this statement valid?

(b) If you contend the statement is valid, how do you know?

(c) If you contend the statement is invalid, what is wrong with it?

(d) If the statement is invalid, restate it to give a valid statement.

(e) Is the valid statement (original, or your revision) a conditional or bi-conditional? How do you know?

(f) Would the following investigation test, i.e. provide data to either support or contradict, the valid hypothesis (either the original or your revision), or will it fail to test the hypothesis? Explain.

A person runs a ski mobile on a frozen lake varying how the speed changes during the runs for 24 trials and measures the net force that acts on the ski mobile. Each time she finds if the speed changes there is net force.

Mirage. The figure below shows a simplified situation of a mirage. The air is

stratified into three layers with refractive indices ni with i = 1, 2, 3. The continuous

variation of refractive index with height on a hot day is similar for n3 > n2 > n1.

The bottom two layers have a thickness of a and b, respectively. An observer

at height h is looking at a tree of height H. Calculate the minimum horizontal

distance between the tree and the observer so that the observer sees a mirage. Take

n3 = 1.01, n2 = 1.02, n3 = 1.03, a = b = 0.5 m, h = 2 m, and H = 10 m.

A Young’s-double-slit experiment is performed with two wavelengths - 400 and 800

nm. Assume that both sources are perfectly coherent with each other and have

equal intensity. Calculate the light-intensity pattern on a screen placed 1 m from

the slits, which are separated by a distance of 1 cm.

Two plane waves of light with wavelength 500 nm are incident on a screen. If the

spatial resolution of the detector is 0.1 mm, what is the maximum angle between

the two waves for which we can resolve the fringes. Assume we can resolve fringes if

the distance between the maxima and minima is equal to the detector resolution.

A uniform meter rule AB is balanced on a knife edge placed 58cm from A when a mass of 20.0Kg is placed 25cm from B. Calculate the mass of the rule and the force exerted on the rule by the knife edge

A mechanism using a wrench of length 28cm to loosen a nut exert a force of 15N at the end of the handle at 40 degrees with the handle of the wrench. What torque does the mechanist exert about the center of the nut

 How long will it take a drop of dextrose from a bottle 2.30 m high hit the floor?

A 60-kg high-diver starts his dive at a height of 20 m.

a. What is his total mechanical energy at the start of his dive?

b. What is his velocity halfway into the dive?

c. What is his velocity just before hitting the water below?

A 20-kg child on a swing can make a maximum angle of 400 with respect to the vertical. What is the child’s maximum speed if the chains of the swing have a length of 4 m?

A 60-kg high-diver starts his dive at a height of 20 m.

a. What is his total mechanical energy at the start of his dive?

b. What is his velocity halfway into the dive?

c. What is his velocity just before hitting the water below?