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

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uwostudent70

4 Jan 2021

School

Western University

Department

Kinesiology

Course

Kinesiology 2241A/B

Professor

Thomas Richard Jenkyn

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Document Summary

Physics definition a force is an action that causes mass to be accelerated. Isaac newton"s 3 laws: objects don"t want to be accelerated because objects possess inertia, the force required to accelerate an object is proportional to its mass f = (m)(a) If a force is applied to an object, the object pushes back with the same force. Mass is not a vector, it is a scalar so it only has one property. Mass has a magnitude measured in kilograms (kg) The amount of matter that makes up an object is its mass (measured in kg) Gravity pulls all objects toward the center of the earth with a force that has magnitude f = (m)(g) The force that gravity pulls on the object with is the weight of the object measured in newtons (n), or pounds (lbs) in the imperial system. Mass and weight are not the same thing. Since a force is a vector quality, it has 4 properties.

Related Questions

1) An object is moving with constant velocity. Which of the following statements is true?
a) A constant force is being applied in the direction of motion.
b) A constant force is being applied in the direction opposite of motion.
c) There are no forces acting on the object.
d) The net force on the object is zero.
e) There is no frictional force acting on the object.

2) You apply the same force to two objects. Object 1 has mass M and object 2 has mass 5M. The acceleration is
a) ten times that of object 1 b) five times that of object 1
c) the same as that of object 1 d) 1/5 as that of object 1

3) An object of weight W is in free-fall close to the surface of Earth. What is the force that the object exerts on Earth?
a) a force greater than W b) a force less than W
c) a force equal to W d) no force at all

4) A parking crate slides down an inclined ramp at constant velocity. Thus we can deduce that _
a) a frictional force is acting on it
b) a net downward force is acting on it
c) a net upward force is acting on it
d) it is not acted on by appreciable normal force
e) it is not acted on by appreciable gravitational force

5) A person applies a constant force of 20N to a rock of mass 1000kg for a total of 20 seconds. What is the work done by this person if the person does not move at all by this applied force?
a) 1000J b) 2000J c) 20,000J d) 0J e) 400J

6) If the net work done on an object is positive, then the object's kinetic energy.
a) decreases b) remains the same c) increases d) is zero

7) You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.
a) Work is + on the way up and + on the way down
b) Work is + on the way up and - on the way down
c) Work is - on the way up and + on the way down
d) Work is - on the way up and - on the way down

lavenderbat941

1) An object is moving with constant velocity. Which of thefollowing statements is true?
a) A constant force is being applied in the direction ofmotion.
b) A constant force is being applied in the direction opposite ofmotion.
c) There are no forces acting on the object.
d) The net force on the object is zero.
e) There is no frictional force acting on the object.

2) You apply the same force to two objects. Object 1 has mass M andobject 2 has mass 5M.
a) ten times that of object 1 b) five times that of object 1
c) the same as that of object 1 d) 1/5 as that of object 1

3) An object of weight W is in free-fall close to the surface ofEarth. What is the force that the object exerts on Earth?
a) a force greater than W b) a force less than W
c) a force equal to W d) no force at all

4) A parking crate slides down an inclined ramp at constantvelocity. Thus we can deduce that _
a) a frictional force is acting on it
b) a net downward force is acting on it
c) a net upward force is acting on it
d) it is not acted on by appreciable normal force
e) it is not acted on by appreciable gravitational force

5) A person applies a constant force of 20N to a rock of mass1000kg for a total of 20 seconds. What is the work done by thisperson if the person does not move at all by this appliedforce?
a) 1000J b) 2000J c) 20,000J d) 0J e) 400J

6) If the net work done on an object is positive, then theobject's kinetic energy.
a) decreases b) remains the same c) increases d) is zero

7) You throw a ball straight up. Compare the sign of the workdone by gravity while the ball goes up with the sign of the workdone by gravity while it goes down.
a) Work is + on the way up and + on the way down
b) Work is + on the way up and - on the way down
c) Work is - on the way up and + on the way down
d) Work is - on the way up and - on the way down

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.

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

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