[pleasehelpmetoo]

Hey guys,
Some questions that have been bugging me...
Mass of spacecraft is 11,000kg, and the mass of an outside astronaut is 92kg.astronaut exerts a force of 36N on spacecraft by pushing it.
Find the acceleration of the spacecraft and astronaut.
I cannot understand this question.

A 0.22 rifle bullet,travelling at 350 metres per second strikes a block of wood and penetrates to a depth of 0.13 metres
The block is clamped to a bench so that it doesn't move.
Mass of bullet is 1.8g
How much time is required for bullet to stop?
Determine the force in newtons that the bullet exerts on the block.

Any help with even understanding these questions would be greatly appreciated.:)

[ebaines]

First question: simply use F=ma to determine the astronaut's acceleration. He pushes on the spacecraft with a force of 36N, which means the spacecraft pushes back on him with 36N, so now you can calculate his acceleration.

Second question: start with the formula v(final)^2 - v(init)^2= 2ad. Here you know v(init) = 350 m/s, v(final) = 0, and d = 0.13m, so you can calculate the bullet's acceleration, which will turn out to be a negative number since the bullet is decelerating. Then you can determine the time it takes to decelerate by using v(final) - v(init) = at. Finally, you can get the force exerted on the bullet from F=ma. A negative value of F means that the force is causing the bullet to slow down.

[Perito]

mass of spacecraft is 11,000kg,
mass of an astronaut is 92kg.
astronaut exerts a force of 36N on spacecraft

(equation 1)

F = force, m = mass, a=acceleration.



Solve for a.
A Newton is equivalent to a kg-m/sec^2. So, the acceleration will be found in m/sec^2.

If the astronaut pushes on the spacecraft with a force of 36N, then the spacecraft will push back on the astronaut with the same force (but opposite direction). The astronaut will also be propelled backward. However, since his mass is smaller, his acceleration will be much larger.