# Maths Homework Question Related to Physics

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.

• Firstly, this is a physics question. Secondly, in your first sentence, you seem to imply that mathematics is calculations - and that is not correct. Finally, your error is not in your calculations, but in your setup. The relevant ideas are conservation of energy, potential energy, and kinetic energy. You don't need to use any kinematics – davidlowryduda Oct 19 '13 at 2:41
• I keep getting the answer 30m/s but it says it is incorrect – Sherry Eskandarian Oct 19 '13 at 3:42
• I got the answer, thank you – Sherry Eskandarian Oct 19 '13 at 3:58