Question no 9) A package is dropped from a helicopter moving upward at 15m/s If it takes16 sec before the package strikes the ground, how high above the ground was the package when it was released if air resistance is negligible?
Ans) 1000m
Question no. 11) If A -B = 0, then the vectors A and B have equal magnitudes and are directed in the opposite directions from each other.
Ans) False
Question no. 16) A monkey is sitting at the top of a tree 20 m above ground level. A person standing on the ground wants to feed the monkey. He uses a bow and arrow to launch the food to the monkey. If the person knows that the monkey is going to drop from the tree at the same instant that the person launches the food, how should the person aim…show more content…
Ans) 4.8seconds
Question no 4) A man is straining to lift a large crate, without success because it is too heavy. We denote the forces on the crate as follows: P is the upward force the man exerts on the crate, C is the vertical contact force exerted on the crate by the floor, and W is the weight of the crate. How are the magnitudes of these forces related while the man is trying unsuccessfully to lift the crate?
Ans) P+C=W unit of force is Newton(N)
Test 3:
Question no.5)Jacques and George meet in the middle of a lake while paddling in their canoes. They come to a complete stop and talk for a while. When they are ready to leave, Jacques pushes George's canoe with a force F to separate the two canoes. What is correct to say about the final momentum and kinetic energy of the system if we can neglect any resistance due to the water?
The final momentum is in the direction opposite to F but the final kinetic energy is zero.
Question no. 10) A person pushes horizontally on a heavy box and slides it across the level floor at constant velocity. The person pushes with a 60.0 N force for the first 6.88M at which time he begins to tire. The force he exerts then starts to decrease linearly from 60.0 N to 0.00 N across the remaining 6.88M How much total work did the person do on the box?
619J(Joules)
Question no 12) In the figure, determine
- A Man Is Attempting To Lift A Crate Using A Two Part Pulley System
- A Man Is Attempting To Lift A Crate
- A Man Is Attempting To Lift A Crate Using
A crate on rollers is pushed up an inclined plane into a truck. The pushing force required is less than half the force that would be needed to lift the crate straight up into the truck. Does the inclined plane serve as a simple machine in this situation? In pushing a heavy box across the floor, is the force you need to apply to start the box moving greater than, less than, or the same as the force needed to keep the box moving?On what are you basing your choice? How do you think the force of friction is related to the weight of the box? Man Crates has the best, most unique gifts for guys. Our crates, ammo cans, project kits, and concrete bricks are packed with snacks, gadgets, and gear that guys love. So sit back, relax, and enjoy looking like a gifting guru, because Man Crates has you covered!
Lifting heavy items is one of the leading causes of injury in the workplace. In 2001, the Bureau of Labor Statistics reported that over 36 percent of injuries involving missed workdays were the result of shoulder and back injuries. Overexertion and cumulative trauma were the biggest factors in these injuries. Bending, followed by twisting and turning, were the more commonly cited movements that caused back injuries. Strains and sprains from lifting loads improperly or from carrying loads that are either too large or too heavy are common hazards associated with manually moving materials.
When employees use smart lifting practices, they are less likely to suffer from back sprains, muscle pulls, wrist injuries, elbow injuries, spinal injuries, and other injuries caused by lifting heavy objects. Please use this page to learn more about safe lifting and material handling.
Lifting Principles
A Man Is Attempting To Lift A Crate Using A Two Part Pulley System
Lifting Stages
- Preparation
- Lifting
- Carrying
- Setting Down
1. Preparation
Before lifting or carrying, plan out your lift. Think about:
- How heavy/awkward is the load? Should I use mechanical means (e.g. a hand truck) or another person to help me with this lift? Is it possible to break the load into smaller parts?
- Where am I going with the load? Is the path clear of obstructions, slippery areas, overhangs, stairs, and other uneven surfaces? Are there closed doors that need to be opened?
- Are there adequate handholds on the load? Do I need gloves or other personal protective equipment? Can I place the load in a container with better handholds? Should another person help me with the load?
2. Lifting
Get as close to the load as possible. Try to keep your elbows and arms close to your body. Keep your back straight during the lift by tightening the stomach muscles, bending at the knees, keeping the load close and centered in front of you, and looking up and ahead. Get a good handhold and do not twist while lifting. Do not jerk; use a smooth motion while lifting. If the load is too heavy to allow this, find someone to help you with the lift.
3. Carrying
Do not twist or turn the body; instead, move your feet to turn. Your hips, shoulders, toes, and knees should stay facing the same direction. Keep the load as close to your body as possible with your elbows close to your sides. If you feel fatigued, set the load down and rest for a few minutes. Don’t let yourself get so fatigued that you cannot perform proper setting down and lifting technique for your rest.
4. Setting Down
Set the load down in the same way you picked it up, but in the reverse order. Bend at the knees, not the hips. Keep your head up, your stomach muscles tight, and do not twist your body. Keep the load as close to the body as possible. Wait until the load is secure to release your handhold.
Important Things To Remember
- Use mechanical means (e.g. hand trucks, pushcarts, etc.) when possible for heavier or awkward loads. Remember to obtain training and authorization before using a forklift.
- It is easier and safer to push than to pull.
- Keep loads as close to the body as possible and do not twist while lifting, carrying, or setting down a load. Nose, shoulders, hips, and toes should all be facing the same direction.
- Minimize reaching.
- As a general rule, bend at the knees, not the hips.
- Get help when needed. Do not lift or carry things you don’t feel comfortable with, no matter how light the load.
- Plan ahead for all parts of the lift: lifting, carrying, and setting down.
- Try to utilize proper handholds while lifting. If an item does not have a good handhold, think of ways to remedy this, such as placing the item in a container with good handholds, creating a safe and proper handhold with an appropriate tool, etc.
- Use personal protective equipment where needed, such as gloves with good grip and steel-toed boots where appropriate.
- Implement rest breaks and job rotation for frequent and/or heavy lifting.
- Place items to be lifted within the “power zone”. The power zone is close to the body, between the mid-thigh and mid-chest of the person doing the lifting. This is the area where the arms and back can lift the most with the least amount of effort.
Weight Of Objects
Heavier loads place greater stress on muscles, discs, and vertebrae.
A Man Is Attempting To Lift A Crate
Where possible, use mechanical means such as forklifts or hand trucks to transport heavy items. Ramps can be helpful in moving heavy items from one level to another. Materials that must be manually lifted should be placed at “power zone” height: about mid-thigh to mid-chest of the person doing the lifting. Ensure that proper lifting principles (see above) are used. Try to order supplies in smaller quantities and/or break loads up into smaller, lighter quantities where possible. Is the container itself heavy? Perhaps a smaller or lighter container is available. Limit weight you lift to no more than 50 pounds. When lifting loads heavier than 50 pounds, use two or more people to lift the load.
Awkward Postures
Bending while lifting causes several problems for the back. It adds the weight of the upper body to the weight of the object being lifted. Bending and/or reaching moves the load away from the body and allows leverage to significantly increase the effective load on the back, leading to stress on the lower spine and muscle fatigue. Carrying loads on one shoulder, under an arm, or in one hand creates uneven pressure on the spine.
Move items close to the body and use the legs when lifting from a low location to minimize bending and reaching. Ensure proper housekeeping is taking place so that you may get as close to your lifting load as possible. Store and place materials that need to be manually lifted at the “power zone”: mid-thigh to mid-chest height. This can be accomplished by placing objects on shelves, tables, racks, or stacked pallets; or by using ladders or aerial lifts where necessary to elevate yourself and minimize overhead reaching. Roll-out decks in truck beds can be utilized to bring materials closer to the employee and eliminate the need to crawl into the back of a truck. Ensure that proper lifting principles (see above) are used, including avoiding twisting and holding the load close to the body.
High-Frequency and Long-Duration Lifting
Holding items for long periods, even if loads are light, increases the risk of back and shoulder injury since muscles can be starved of nutrients and waste products can build up. Repeatedly exerting, such as when pulling wire, can fatigue muscles by limiting recuperation times. Inadequate rest periods do not allow the body time to recover.
Plan ahead when beginning work that will require high-frequency and long-duration lifting. This way, the work can be organized in such a way so as to minimize the time workers spend holding loads. Adequate rest breaks can be planned in, as well as job rotation between employees. This includes both rotating tasks (employees trade off on differing tasks) and team work (two or more employees work together doing different parts of the same activity to reduce strain). Planning can also include the pre-assembly of work items to minimize the time spent handling them during the actual work.
A Man Is Attempting To Lift A Crate Using
Inadequate Handholds
Inadequate handholds, such as boxes without handles or oddly-shaped loads, make lifting more difficult, move the load away from the body, lower lift heights, and increase the risk of contact stress and of dropping the load.
Where possible, utilize handholds such as handles, slots, or holes that provide enough room for gloved hands. Try to use materials that are packaged with proper handholds (your supplier may be able to provide different containers), or move materials into containers with good handholds. Wear protective equipment to avoid finger injuries and contact stress. Ensure that gloves fit properly and provide adequate grip. Suction devices are helpful in lifting junction boxes and other materials with smooth, flat surfaces. Other tools may be available that can create temporary handles.
Environmental Factors
Be aware of extreme temperatures that can affect lifting and material handling. For example, muscle flexibility decreases in cold temperatures, and hot temperatures can lead to heat stress. Low visibility or poor lighting increases the chance of trips and falls.
Do what you can to adjust work schedules to minimize exposure to extreme temperatures or low visibility. Wear appropriate clothing for the temperature in which you will be working. Drink lots of water to avoid dehydration in excessive heat. Provide proper lighting for areas with low light and try to perform work during daylight hours when possible.
Additional Resources
- OSHA Ergonomics eTool: Materials Handling: Heavy Lifting
- OSHA Ergonomics eTool: Ergonomic Principles Index – Lifting
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