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?
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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
A 60 kg skier is coasting down a 30° slope. Near the top of the slope, her speed is 4.0 m/s. She accelerates down the slope due to the gravitational force, but she is also experiencing a friction force with a magnitude of 80 N apposing her motion. Ignoring air resistance, what is her speed once her displacement is 70 m along the path of travel?
To check your answers:
1. What are the SI units for momentum?
You correctly answered kg*m/s. The SI unit for momentum is a combination of the kilogram (kg) for mass and meter per second (m/s) for velocity.
2. Which of the following is not involved in hitting a tennis ball?
You chose option B, chemical potential energy. This is the correct answer. When hitting a tennis ball, kinetic energy, gravitational potential energy, and elastic potential energy are all involved, but chemical potential energy is not.
3. How much power is required to lift a 2.0 kg mass at a speed of 2.0 m/s?
You answered 4.0 J. This answer is incorrect. Power is measured in watts (W) and is calculated by dividing the work done by the time taken. To find the power required to lift the mass, you need to calculate the work done, which is equal to the force multiplied by the distance moved. Since the velocity is given, you can calculate the force required to lift the mass against gravity using the equation F = mg, where m is the mass (2.0 kg) and g is the acceleration due to gravity (approximately 9.8 m/s^2). Once you find the force, you can multiply it by the velocity to find the power. The correct answer can be calculated as follows:
Work (W) = Force (F) * Distance (d)
Force (F) = mass (m) * acceleration due to gravity (g)
Power (P) = Work (W) / Time (t)
Substituting the values:
Force (F) = 2.0 kg * 9.8 m/s^2 = 19.6 N
Work (W) = 19.6 N * 2.0 m = 39.2 J
Power (P) = 39.2 J / time (not given)
Therefore, the correct answer cannot be determined without knowing the time taken (in seconds).
So, in summary, your first and second answers were correct, but the third answer needs to be rechecked and calculated using the given equations.