Fundamentals:Skills Physics: The mechanics of the Human Body

Where is the best place to have one's center of mass?​

Directly over their feet If the center of mass of a person is directly over their feet, they will have better balance.​

What is being calculated when mass is multiplied by the acceleration? ​

Newton's Second Law Newton's second law of motion is mass times acceleration.

What is the best description of the conservation of momentum?​

The momentum before a collision is the same as the momentum after a collision.

If two cars collide, what do the laws of physics tell us?

The momentum before the collision is the same as the momentum after the collision. Momentum is conserved in every collision. It does not disappear, increase, or decrease.​

What is the equation for torque?​

force x distance Torque can be defined as a force acting at a distance.Torque = force x distance

What is the best description of torque?​

A force which may cause an object to rotate

A 100 kg client felt 100 N of force. What was the acceleration of the client?

1 m/s2 Force is equal to the mass times the acceleration. ​ Therefore, 100 N = 100 kg x acceleration. So, acceleration = 100 N ÷ 100 kg = 1 m/s2

If a box on a lever has 100 N x m of torque and is 60 N, how far is it from the pivot point?

1.67 meters Torque is equal to the force times the distance. 100 N per m = 60 N x distance​ Therefore, the distance = 100 N per m ÷ 60 N = 1.67 m

If two medical professionals can lift 500 N each, what is the maximum force they can lift together?

1000 N Two forces pulling in the same direction are added together. ​ 500 N + 500 N = 1000 N

A 100 kg person is moving at 2 meters per second. They bump into a person who is standing without moving and weighs 50 kg. They transfer all their momentum to the 50 kg person. What is the speed of the 50 kg person after the collision?

4 m/s Person A's momentum or total momentum : MA x VA = 100 kg x 2 m/s = 200 kg per m/s​ After the collision, Person A transfers all their momentum to Person B (the 50 kg person), so Person B starts to move, while Person A stops. Person B's momentum = Person A's momentum (total momentum) = 200 kg per m/s​ Because momentum equals mass times velocity: 200 kg per m/s = MB x VB​ Because Person B weighs 50 kg: VB = 200 kg per m/s ÷ MB Therefore, ​Person B's velocity: VB = 200 kg per m/s ÷ 50 kg = 4 m/s

How much torque does a 20 N box create when it is two meters from the pivot point?

40 N x m Torque is equal to the force times the distance to the pivot. 20 N x 2 m = 40 N per m Torque = force x distance

A person of 100 kg is moving at 0.5 m/s. What is their momentum?

50 kg per m/s Momentum is mass times velocity. Therefore, the person's momentum is: M x V = 100 kg x 0.5 m/s = 50 kg per m/s

A client who weighs 1000 N needs to be lifted onto a gurney. How much extra force is applied to the healthcare professional's joints when lifting the client with the help of a colleague if the weight is distributed equally between the two?

500 N According to Newton's third law, for every force, there is an equal and opposite reaction force between two interacting bodies. Therefore, in this scenario, the force for the two healthcare professionals to lift the client equals the force that the client puts on the two healthcare professionals' joints. And the client's force is his weight: 1000 N. Therefore, if two people share a 1000 N load, then each person is adding 500 N of force to their body. 1000 N ÷ 2 = 500 N

An unfortunate client is in a car accident. The police officer mentions the car was going 15 m/s and came to a stop in two seconds. The client is 100 kg. How much force did the client experience during the accident? Recall that acceleration is equal to the change in speed divided by the time taken and force is equal to mass times acceleration.

750 N The client sitting in the car has the same speed as the car. They start at 15 m/s and then stop at 0 m/s. This motion finishes in 2 seconds. Recall that acceleration is the change in speed divided by the time taken. Therefore, the acceleration for this client during this motion is: (15-0) ÷ 2 = 7.5 m/s2. The client's weight (or mass) is 100 kg. Recall that force is equal to mass times (x) acceleration. Therefore, the force that this client experiences during the motion (from having the same speed as the car to a complete stop) is: 100 x 7.5 = 750 N.

Newton's second law of motion is best described by which statement?

Force = mass x acceleration Newton's second law states that the force on any object is equal to the mass of the object multiplied by the object's acceleration.

Which action should the medical professional perform in order to lift a client?​

Hold the client so that the center of mass is over the feet To lift a heavy weight, one should hold the weight such that its center of mass is over their feet. Medical professionals should not cross their legs before attempting to lift a client. It may increase the chances of losing their balance and falling.