[rickyraz91]

1. How far (in meters) must a 600 kg pile driver fall, if it is to do 14000 J of work?

2. A spring whose spring constant is 150 N/m is compressed 0.800 m. What speed (in meters/second) can it give to a 0.600 kg ball when released?

3. A 550 N crate rests on the floor. How much work in joules is required to move it at constant speed 4.0 m along the floor, against a friction force of 140 N?

4. What is the minimum work in joules needed to push a 1710 kg car 74.0 m up a 12.5 degree incline? (Ignore friction.)

5. How much work in joules must be done to stop a 3000 kg car traveling at 150 km/hr?

6. A 1620 kg car rolling on a horizontal surface has a speed of 70 km/hr when it strikes a horizontal coiled spring and is brought to rest in a distance of 5.5 m. What is the spring constant (in N/m) of the spring? (Ignore nonconservative forces such as friction.)

7. A spring has a spring constant "k" of 160 N/m. How much must this spring be compressed (in meters) to store 70 J of energy?

8. Tarzan is running at a top speed of 5.0 m/s and grabs a vine hanging vertically from a tall tree in the jungle. How high (in meters) can he swing upward?

9. An object slides down a frictionless 33 degree incline whose vertical height is 87.0 cm. How fast is it going in meters/second when it reaches the bottom?

10. A 33 kg child descends a slide 7.8 m high and reaches the bottom with a speed of 3.30 m/s. How much thermal energy (in joules) due to friction was generated in this process?

11. Two railroad cars, each of mass 6800 kg and traveling 80.0 km/hr, collide head-on and come to rest. How much thermal energy in joules is produced in this collision?

[Wondergirl]

Have you tried to work out any of these? If so, what answers did you get? (We won't DO your homework for you here, but we will help with any parts you don't understand.)

[rickyraz91]

Yea I did I got 7,10,11 but cannot figure out the rest can you help?

[Unknown008]

1. Come on, use the formula for work done.

2. Find the elastic potential energy stored by the spring.From the elastic potential energy you got, you can find the maximum speed, using the kinetic energy formula.

3. Find the work done due to friction. Since there is no acceleration, the resultant force is 0, and hence, the force applied is equal to the frictional force. Use the work equation again to find the work done, since you now know the applied force.

4. Work out the gravitational force that acts on the car along the plane by resolving the weight of the car. Then, use the work formula to find the work done.

5. Since you need to stop the car, you have to decrease it's kinetic energy to zero. How much energy do you have to remove? Use the formula for kinetic energy.

6. Find the kinetic energy of the car. This energy is transferred to the spring. Using the elastic potential energy formula, find the force that is applied on the spring. From that, you can use Hooke's Law to find the elastic constant of the spring.

8. Find his kinetic energy in terms of a variable, say 'm'. Then, convert that energy into gravitational potential energy. The variable 'm' should cancel, leaving you're the maximum height he gets to.

9. Find the gravitational potential energy the body possesses at the top of the plane. Convert all this into kinetic energy. Then, use the formula for kinetic energy to solve for the velocity of the body.

Now, since you said that you did 7, 10 and 11, can you post the answers you got? Because I don't understand how you can get those answers if you didn't do the simplest ones.

[rickyraz91]

I got 5 also
I looked what you told me to do but I can't still get it. Please can you please just work them out with me pleasee.

[Unknown008]

i got 5 also i looked what you told me to do but i can't still get it. please can u please just work them out with me pleasee.

Okay, but post what you did! I want to know where you are stuck, to find the best way to make you understand, and better, so that you know next time how to do it.