An astronaut weighing 190 lbs on Earth is on a mission to the Moon and Mars. Required:
a. What would he weigh in newtons when he is on the Moon?
b. How much would he weigh in newtons when he is on Mars, where the acceleration due to gravity is 0.38 times that on Earth?

The weight is defined as:

W = m*g

where:

m = mass

g = gravitational acceleration.

We know that in Earth the astronaut weights 190 lb-f (this is force, not mass, the correct unit here is 190 lb*m/s^2)

then:

190 lb*m/s^2 = m*9.8m/s^2

(190 lb*m/s^2)/(9.8m/s^2) = 19.39 lb

Now we know the mass of the astronaut.

a) wieght on the moon in Newtons.

Newtons uses kilograms as the units of mass, then we need to rewrite the mass of the astronaut in kg.

we know that 1lb = 0.454 kg

Then 19.39 lb is equal to: 19.39*0.454 kg = 8.8 kg

We know that the acceleration due to gravity on the Moon is one-sixth that on Earth.

then: g = (9.8m/s^2)/6

And the weight of the astronaut in the moon will be:

W = 8.8 kg*(9.8m/s^2)/6 = 14.37 N

b) The weight on mars, where the acceleration due to gravity is 0.38 times that on Earth, we have:

g = (9.8m/s^2)*0.38

then the weight will be:

W = 8.8kg*(9.8m/s^2)*0.38 = 32.77 N

the velocity you are looking for is made up of two parts: horizontally velocity, vh, and its vertical velocity, vv. the actual velocity of the ball will be these two parts added together, and because velocity is a vector then they will need to be added vectorially.  

neglecting air resistance etc etc.,  

the horizontal velocity component will be constant (because there is no accelerating force in the horizontal direction.  

vh = 8 ms-1  

the vertical velocity component has an accelerating force: 'g'.  

using v = u +at where a = g = 9.81 ms-2.  

the vertical component of velocity, vv = 0 + gt = vv =9.81 x 2  

vv = 19.62 ms-1 . the zero appears because the virtical component of velocity at time t=0 is zero. remember, the ball was thrown horizontally.  

how fast it will be moving (it actual path (being a parabola )) will be the vector sum of these two.  

adding vectorally gives: -  

v = sqr root (8^2 + 19.62^2) = sqr root(64+384.9) = 21.18 or 21.2 ms-1

myth. it was once thought that animals, including cats and dogs, could only see in black and white. however, scientists have proven this to be a myth. in all animals, including humans, the perception of colour is determined by the presence of cells in the eye called cone photoreceptors.