science - expantion and contraction

An object of mass 20kg is falling in air and experiences a force due to air resistance of 40N. Determine the net force acting on the object and calculate the acceleration of the object.

The length of the wing of an air plane is 10 m. Its horizontal velocity is 200 m /s. If the vertical component of the earth’s magnetic field is 5.0 × 10^-5 weber /m2, calculate the potential difference developed across the two ends of the wing.

an L.E.D bike light that produces 95% light and only 5% heat

A track team is practicing for a 4 x 100 m relay race. The first runner, Linda, is running at a constant speed of 8.6 m/s. The next runner, Jenny, will be starting from rest at the 80 m mark. She has an acceleration of 1.0 m/s2. Ideally the two runners meet at the 100 m mark to hand over the baton. At this point, Jenny is still accelerating.

a) At what distance behind Jenny should Linda be when Jenny starts running? (Assume for simplicity that there is no distance between the two runners when the switch happens.)

b) How long does it take Jenny to run from the 80-m mark to the 100-m mark?

c) What’s Jenny’s speed at the 100m mark? Linda Jenny

deduce expression for resistance

the displacement of an object of mass m after time t when a net force F acts on it is dependent on F, t and m. use dimensional analysis to work out the formula for the displacement of the object.

i dont understand halflife. I just dont understand the concept but i understand radioactive decay.

I need to know how these work in relation to thermal transfers and the kinetic theory?

A 1000kg car speeds up on the street at 72km/h. It suddenly brakes with a constant force of 5x103 N. How far the car will travel from the moment it brakes till it completely stops?

if a star is 5.2x1016 meters away, what is the parallax angle in degrees?

Just need a step by step answer to confirm that my answer of 0.000165598290 is correct ( note that the second five and zero have a recurring symbol above each)

I used the conversion 1parsec= 3.1x1016m in my calculation

any help would be much appreciated

The following is a summary of a nuclear fission reaction: 235 1 →unknown nucleus A (Equation 1) 92 U On

unknown nucleus A → 90 Sr + unknown nucleus B + 3 1n (Equation 2) 38 O

Can you help find the mass number and atomic number for the unknown nuclei A and B to identify them. can you explain this to me and how you got worked this out, thank you most sicnerely.

I have done some workings but think it may be incorrect

How can we calculate the work done by a tension force a solid at time t ?

Without using your spring scale, estimate the order of magnitude of the mass of your calculator in grams from what you judge to be its size, using the fact that the density of water is 1 g/cm3. Assume that the density of water is about the same as the density of your calculator. 1 g 102 g 104 g 106 g

I need help on understanding what redshift is and what the charts mean

What equal lengths of iron wire and a lead wire, each of 1 mm diameter must be joined in parallel to give an equivalent resistance of 2 ohm ? Resistivity of iron and lead are 10 and 49 micro ohm-cm respectively.

You are in a snowball fight, and throw a snowball at a high angle over level ground. While your opponent is watching this first snowball, you throw a second one at a low angle timed to arrive before or at the same time as the first one.

Assume both snowballs are thrown with a speed of 39.4 m/s. the first one is thrown at an angle of 71 degrees to the horizontal. What angle should the second snowball be thrown to arrive at the same point as the first?

Why does a compass point North & would it also point North on the Moon if there is a North on the Moon?

http://www.open.edu/o.../content-section-1.1 Figure 8 please need help fast thanks