This is a physics question, but it's calculations.
A 15kg child slides down a 2.3m -high playground slide. She starts from rest, and her speed at the bottom is 2.1m/s .
What is the change in the thermal energy of the slide and the seat of her pants? (2.s.f.)
I used the kinematics equation
$$d= \frac{(v_i+v_f)}{2} * (t)$$
$$2.3 = \frac{2.1 \cdot t}{2}$$
$$t= 2.19$$
Then I used t to find acceleration then multiply acceleration with the mass which is 15kg, and then multiply that again by 2.3m to find the change in thermal energy. But I feel like I calculate t incorrectly, because it keeps telling me it's incorrect. The rest is correct, however, the first part is not.
It's conservation of energy -- you don't need any calculus. You know that in the absence of friction energy is conserved. If some energy is lost it must have gone to friction -- a.k.a thermal energy. You know how much energy lost because the child starts at some height from rest. That tells you the initial energy (her potential energy.) I think you can take it from there.