After yesterday's investigation, we learned the formulas to calculate the kinetic energy, the gravitational potential energy and mechanical energy.
Kinetic energy: Ek = 1/2 mv^2
Gravitational potential energy: Eg = mgΔy
Mechanical energy: Emech = Eka + Ega = Ekb + Egb
By using these equations, we can calculate an object's kinetic, gravitational and mechanical energy. The energy change of the system due to a force is called work, and the unit for it is joules (J). 1 kg (m)^2/s^2.
For any free fall object, since gravity is the only source that applies force, so the kinetic energy from the release hand would all turn into gravitational potential energy. For example, a tennis ball weighed 53 g has been dropped from the height of 1.5 m.
Its gravitational potential energy could be calculated in the following way:
W = 0.053 kg (9.8 m/s^2) (1.5 m)
= 0.779 J
And from there we could calculate the final velocity right before the ball touches the ground:
0.779 J = 1/2 (0.053 kg) v^2
v = 5.42 m/s
Something that intrigued me from today's learning is the errors that exists in the experiment. The result from motion detector was very different from the theoretical result that has been calculated. What caused such big error percentage? And how could we reduce the errors in the lab like this?