# Homework Help: Work/enery questions

1. Apr 4, 2005

### joejo

Hi,

1. State the SI units to measure:
a. Work. joules
b. Kinetic Energy. joules
c. Power. watts

2. Calculate the work done by a 140kg black bear that climbs 18m up a tree. 24696J

3. A golf ball is given 115 J of energy by a club that exerts a force over a distance of 4.5cm while the club and the ball are in contact.
a. Calculate the magnitude of the average force exerted by the club on the ball.
b. If the ball’s mass is 47g, find the magnitude of its average acceleration.
c. What speed does the club impart to the ball? for 3.....i got 2555.56N

4. A 55kg diver has 1.62 kJ of gravitational potential energy relative to the water when standing on the edge of a diving board. How high is the board above the water? 3.01m

5. Calculate the power of a light bulb that transforms 1.5x104 J of energy per minute. 250w

6. A chair lift takes skiers to the top of a mountain that is 320 m high. The average mass of a skier complete with equipment is 85 kg. The chair lift can deliver three skiers to the top of the mountain every 35s.
a.Determine the power required to carry out this task. (Assume the skiers join the lift at full speed.)
b.If friction increases the power required by 25%, what power must the motors running the lift be able to deliver?

for 6.....
Eg=mgh
=85kg*9.8N/kg*320m
=266560J 2.7*10 to the 5

or

Ek= 1/2mvsquared
= ½(85kg) (9.1m/s)
=3519.43J

for 6.b)

im thinking....
=53312J

dont understand how to do 6 and 3 and also, if they rest are right?!

2. Apr 4, 2005

### ek

Q6 is asking for the power, not energy.

P = mgh/t

And for Q6b, I'd assume the answer is just 5mgh/4t.

Edit: And remember there are three skiers at 85kg each, not just one.