Kinesiology 2241A/B Lecture Notes - Lecture 8: Body Force, Biceps, Resultant Force

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copperlizard489

1 Feb 2018

School

Western University

Department

Kinesiology

Course

Kinesiology 2241A/B

Professor

Thomas Richard Jenkyn

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Document Summary

What is a force: a force is an action that causes mass to be accelerated. Common definition: a push or pull, a rub or pressure, a blow or impact, gravity. Isaac newton"s 3 laws: objects (like the soccer ball) don"t want to be accelerated because objects possess inertia, the force required to accelerate an object is proportional to its mass f= m x a. Force and acceleration has a direction and a magnitude making them vectors mass only has a magnitude (kg) making it a scaler. Scaler"s only have 1 property: mass has a magnitude measured in kilograms (kg) Mass, weight and gravity: the amount of matter that makes up an object is its mass. Newtons (n), or pounds (lbs. ) in the imperial system: mass and weight are not the same thing. Basketball in hand: force has a line of action, draw las the dotted line below. Center of mass: gravity is a body force.

Related Questions

1. A force is a vector quantity because it has both

A) mass and acceleration.

B) action and reaction counterparts.

C) magnitude and direction.

2. If an object's mass is decreasing while a constant force is applied to the object, the acceleration

A) remains the same.

B) decreases.

C) increases.

3. For an action force, there must be a reaction force that

A) is exactly equal in magnitude.

B) always acts in the same direction.

C) is slightly smaller in magnitude than the action force.

D) is slightly larger in amplitude than the action force.

4. A baseball player bats a ball with a force of 1000 N. The reaction force that the ball exerts against the bat is

A) more than 1000 N.

B) less than 1000 N.

C) 1000 N.

D) impossible to determine.

5. If you push an object a given distance, while applying twice the force, you do

A) twice as much work.

B) four times as much work.

C) half as much work.

D) the same amount of work.

6. A job is done slowly, while an identical job is done quickly. Both jobs require the same amount of work, but different amounts of

A) effort

B) power

C) energy

D) none of these

crimsonbear569

1. Which of the following describes an object with a non-zero netforce acting on it? Choose all that apply.
The moped accelerated while making a left turn.
The motorcycle traveled at a constant speed while making au-turn.
The truck slowed down while making a right turn.
The spaceship traveled at a constant speed in a straightline.
The car sped up from 50 mph to 65 mph while moving in a straightline.

2. If you observe that an object is accelerating, what should youconclude?
A non-zero net force is acting on it. Only forces causeacceleration. As such, if an object is accelerating it must bebecause a non-zero net force is acting on it.
It must be in free fall.
It must be changing direction. Acceleration is a vector and vectorshave both magnitude and direction. Thus if an object isaccelerating it must be changing direction.
The forces acting on the object must be greater than the forces theobject is exerting.
It must be speeding up. If an object is accelerating that means itis speeding up.

3. Which of the following are true according to Newton's 2nd Law?Choose all that apply.

If the acceleration is zero, then the net force is zero.
If you apply the same force to 2 objects, the one with more masswill have a greater acceleration.
If you apply the same force to 2 objects, the one with less masswill have a greater acceleration.
If two objects have the same acceleration, the one with less masswill have a larger net force exerted on it.
If two objects have the same acceleration, the one with more masswill have a larger net force exerted on it.
The larger the net force on an object is, the larger theacceleration.
The larger the net force on an object is, the smaller theacceleration.

4. A box is on the Moon. The box weighs 152 lb and is in free fall.How much force is the box exerting on the Moon and in whatdirection?

lb
Up
Down
Right
North
East
West
Left
South

5. Which of the following are the correct units for mass? Chooseall that apply.
slugs
u
kgÂ·m/s2
g
N
m/s2
oz
lb

6. If an object is traveling in a circle, which of the followingmust be TRUE? Choose all that apply.
The object is slowing down.
The object is speeding up.
The object has a net force acting on it.
The object has a constant velocity.
The object is accelerating.

Question 1 of 7 0.5 Points
A 6 N force acts on a 0.3-kg object for 0.3 seconds. By how muchdoes the object's momentum change (in kg-m/s)?

Question 2 of 7 0.5 Points
A 0.4-kg object is traveling to the right (in the positivedirection) with a speed of 1 m/s. After a 0.2 s collision, theobject is traveling to the left at 3 m/s. What is the magnitude ofthe impulse (in N-s) acting on the object? The answer must bepositive.

Question 3 of 7 1.0 Points
The force shown in the attached figure is the net eastward forceacting on a ball. The force starts rising at t = 0.020 s, fallsback to zero at t = 0.062 s, and reaches a maximum force of 55 N atthe peak. Determine with an error no bigger than 25% (high or low)the magnitude of the impulse (in N-s) delivered to the ball. Hint:Do not use J = F?t. Look at the figure. Find the area of a nearlyequally sized triangle.

Question 4 of 7 1.0 Points
A bat hits a moving baseball. If the bat delivers a net eastwardimpulse of 0.6 N-s and the ball starts with an initial horizontalvelocity of 3.8 m/s to the west and leaves with a 5.2m/s velocityto the east, what is the mass of the ball (in grams)?
Part 5 of 7 -

Question 5 of 7 0.5 Points
The force sensor measures the force on the sensor due to thebumper, but the cart's momentum change arises from the force on thecart due to the bumper. Which of the following facts are needed toassert that the magnitude of these two forces are nearly equal atall times.
1. Their magnitudes differ by the magnitude of the net force on thebumper.
2. The force of friction is small.
3. The net force on the bumper is small.
4. The cart's weight is canceled by the the normal force exerted bythe track.

A. 1, 3

B. 2, 4

C. 3, 4

D. 1, 2

E. 1, 4

F. 1, 2, 3, 4

G. 2, 3

Part 6 of 7 -

Question 6 of 7 1.0 Points
A cart traveling at 0.3 m/s collides with stationary object. Afterthe collision, the cart rebounds in the opposite direction. Thesame cart again traveling at 0.3 m/s collides with a differentstationary object. This time the cart is at rest after thecollision. In which collision is the impulse on the cartgreater?

A. The second collision.

B. Cannot be determined without knowing the mass of the cart.

C. The impulses are the same.

D. The first collision.

E. Cannot be determined without knowing the rebound speed of thefirst collision. Reset Selection

Part 7 of 7 -

Question 7 of 7 0.5 Points
The force vs. time graphs for two collisions are shown. Whichcollision has the largest impulse?

A. The impulse for collision 2 since it lasts longer.

B. Cannot be determined since the masses are unknown.

C. The impulse for collision 1 since it has the larger maximumforce.

D. Cannot be determined since the initial an final speeds areunknown.

E. The impulses are the same.

Kinesiology 2241A/B Lecture Notes - Lecture 8: Body Force, Biceps, Resultant Force

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