physics
posted by y912f on .
please check my answers
what are the SI units for momentum?
kg*m/s
which of the following is not involved in hitting a tennis ball?
a. kinetic energy
b. chemical potential energy
c. gravitational potential energy
d. elastic potential energy
i picked B
How much power is required to lift a 2.0 kg mass at a speed of 2.0 m/s?
4.0 J?
i'm not sure about the last one..thanks for checking:)

How much power is required to lift a 2.0 kg mass at a speed of 2.0 m/s?
4.0 J?

NO
force = 9.81 * 2 Newtons
so power = 9.81*4 Newton meters/sec or Watts 
The first two are correct. For the last one, you have to multiply M g by vertical speed to get power in Watts (Joules per second).
2.0 x 9.8 x 2.0 = ? W