Which is an indication that a chemical change to a substance has occurred?
a.
it changes shape.
b.
new substances are formed.
c.
energy is used or given off.
d.
both b and c

Which of the following is considered to be a vector?               a.  temperature    b.  velocity    c.  time    d.  mass

Polly is pushing a box across the floor with a force of 30 n. the force of gravity is –8 n, and the normal force is 8 n. which value could describe the force of friction if polly could not move the box?

A17,250 kg rocket is pushed with a thrust of 6,450,284 n. what is the acceleration of the rocket?