00 A particle of mass 0.34 kg moving on a frictionless horizontal air track
at 1.2 m/s, collides elastically with a second particle lying at rest. After
the collision, the first particle continues in its original direction at 0.66
m/s. What is the mass of the second particle?

This is for my 8th grade science class, i really don’t understand. can someone me? , lol.

Efficiency is the ratio of to for a system a)power in to power in b)power in to power out c) power out to power out d) power out to power in

Aplayground slide is 8.80 ft long and makes an angle of 25.0° with the horizontal. a 63.0-kg child, initially at the top, slides all the way down to the bottom of the slide. (a) choosing the bottom of the slide as the reference configuration, what is the system's potential energy when the child is at the top and at the bottom of the slide? what is the change in potential energy as the child slides from the top to the bottom of the slide? (include the sign of the value in your answer.)