# Test corrections

Test corrections!!!!

## Homework Statement

1.) a railroad car of mass m is moving with speed v when it collides with and connects to a second railroad car of mass 3m, initially at rest. how do the speed and kinetic energy of the connected cars compare to those of the single car of mass m before the collision.
speed/Kinetic Energy
a.)less,less​
b.)less,the same​
c.) the same, less​
d.) greater, the same​

2.) a ball of mass m and momentum p has kinetic energy equal to which of the following?
a.) 1 p2/2 m​
b.) p2/m​
c.)2 (p2/m)​
d.)1m/2p2

3.) a new planet is discovered that is twice the Earth's mass and twice the Earths radius. On the surface of this new planet, a person who weights 500N on earth would experience a gravitational force of
a.)125N​
b.)250N​
c.)500N​
d.)1000N​

## The Attempt at a Solution

1 is not b
2 is not b
3 is not c

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SammyS
Staff Emeritus
Homework Helper
Gold Member

What have you tried?

Where are you stuck?

Can you give any reasons as to why the listed answers are wrong?

A hint for #2: What is the formula for p? Pk\lug that formula in for p in the four choices. See if any of them result in the formula for kinetic energy.