1.
What is the unit of Power?
Hint.
Choose one of the following.
- Joule (J)
- Watt (W)
- Newton (N)
Exercises 3.4 Exercise
2.
What is the power output of a person of mass 80 kg who can climb on the pine tree with 0.4 m/s.
Hint.
Find the relatin between power and velocity.
3.
What is the power output of a person who can lift 100 kg wheel to 2m height in 4 second.
Hint.
Use the definition of power.
4.
Find the speed of an object which weighs 10N and has the kinetic energy of 20 J.
Hint.
Find mass of the object from its weight using Newton’s II law and then apply kinetic energy formula to find the speed.
5.
A 2 kg ball is pushed by a horizontal force all the way to 4 m on the ground when the ball starts moving with 8 m/s. Find the magnitude of the force.
6.
A 50 kg box is lifted vertically to a height of 10m. Fing the energy spent in this work.
7.
When a cannon shell explodes in mid-air: choose all that applies.
Hint.
- total momentum of the system remains the same.
- total kinetic energy of the system remains the same
- total kinetic energy of the system decreases
- total kinetic energy of the system increases
Answer.
a. and d.
8.
What is the formula for calculating power?
- P = W/t
- P = Fd
- P = KE + PE
- P = IV
Answer.
a.
9.
What is the Law of Conservation of Energy?
- Energy cannot be created or destroyed, only transformed from one form to another.
- Energy can be created or destroyed, but it cannot be transformed from one form to another.
- Energy can only be created, not destroyed or transformed.
- Energy can only be destroyed, not created or transformed.
Answer.
a.
10.
A 500 N box is lifted vertically by a worker to a height of 4 meters. How much work is done by the worker on the box?
11.
Which of the following is a unit of work?
- joule
- watt
- newton
- meter per second
12.
A force of 10 Newtons is applied to an object and it moves 5 meters in the direction of the force. How much work was done?
- 2 Newton-meters
- 5 Newton-meters
- 10 Newton-meters
- 50 Newton-meters
13.
Which of the following is a unit of power?
- joule
- watt
- newton
- meter per second squared
14.
Which of the following types of energy is associated with the motion of objects?
- Kinetic energy
- Potential energy
- Thermal energy
- Electrical energy
15.
An object with a mass of 2 kg is lifted to a height of 5 meters. How much potential energy does it have?
- 5 J
- 10 J
- 20 J
- 50 J
16.
If a ball is dropped from a height of 5 meters, what is its velocity just before it hits the ground? (Assume no air resistance and acceleration due to gravity is \(9.8 m/s^2\text{.}\))
- 9.8 m/s
- 14 m/sJ
- 19.6 m/s
- 24.5 m/s
17.
Which of the following is the formula for momentum?
- \(\displaystyle p = mv\)
- \(\displaystyle F = ma\)
- \(\displaystyle E = mc^2\)
- \(\displaystyle v = d/t\)
