Because you have to study about electricity, first of all, and also need to study about polarity
Answer:
a) 2 m/s
b) i) 
ii) 
Explanation:
The function for distance is 
We know that:
Velocity = 
Acceleration = 
To find speed at time t = 0, we derivate the distance function:

Substitute t = 0 in velocity function:

Velocity at t = 0 will be 2 m/s.
To find the function for Kinetic Energy of the box at any time, t.

We know that 


b. The guitar represents half of the wave length. So the full wave length is 2x0.9m = 1.8m.
Using the given equation, v= λ ∙ f,
the wave is moving back and forth along the string at 1.8 ∙ 256
= 460.8m/s
c. Sound waves travel at 6,000 m/s.
Using the given equation, v=d/t, or d=vt,
train's vibration in 3 seconds travels 6000*3
=18,000m or 18km
Answer:
68.5N
Explanation:
When the dolphin decelerates from 12m/s to 7.5 m/s within 2.3s. Then its acceleration is:

The dolphin has a mass of 35kg, according to the Newton's 2nd law, the force exerted on it must be:
