PHYSICS CHAPTERS 1-4

Two vectors have length 𝑉1 = 3.5 km and 𝑉2 = 4.0 km. Can the magnitude of their vector sum be 0.0 km or 9.0 km. Explain why?

maximum occurs when the vectors are in the same direction, minimum is when they are opposite. 3.5+4= 7 max 4-3.5= .5 min Their magnitude cannot equal 0 or 9

If the force is increased up to 50 N and then decreased back to 20 N, how would you describe the motion of the crate?

moving with constant speed

Four students use different instruments to measure the length of the same pen. Which measurement implies the greatest precision? (a) 160.0mm (b) 16.0cm (c) 0.160 m (d) 0.00016km (e) Need more information

(a) 160.0mm

2. The mean length of an object is 5 cm. Which of the following measurements is most accurate? (a) 4.9cm (b) 4.805cm (c) 5.25 cm (d) 5.4 cm

(a) 4.9cm

Which of the following measurements is most precise? (a) 5.00mm (b) 5.00cm (c) 5.00 m (d) 5.00km

(a) 5.00mm

Which statement is correct for ball thrown upward? Ignore the air resistance.

each second it will lose its speed by 9.8 m/s regardless of the mass

You drop a rock off a bridge. When the rock has fallen 4m, your drop a second rock. As the two rocks continue to fall, what happens to their velocities?

Both increase at the same rate

Newton's Third Law

For every action there is an equal and opposite reaction

Newton's Second Law

Force equals mass times acceleration

If you want to project something furthest as possible, which angle you should use? Explain.

45

Accuracy represents

How close a measurement is to the true value

accuracy

A description of how close a measurement is to the true value of the quantity measured.

The answer for 22.1 × 25 should be, (a) 552.5 (b) 553 (c) 550 (d) 600

(c) 550

The sum of the numbers 436.32, 227.2 and 0.301 in appropriate significant figures is, (a) 663.821 (b) 664 (c) 663.8 (d) 663.82

(c) 663.8

You are adding vectors of length 15 and 40 units. Which of the following chooses are possible resultant magnitudes?

(c)30 (d)40 (e)50

In which of the following cases does a car have a negative velocity and a positive acceleration? A car that is traveling in the

(d) -x direction decreasing in speed

Which is not true about an order-of-magnitude estimation? (a) It gives you a rough idea of the answer (b) It can be done by keeping only one significant figure (c) It can be used to check if an exact calculation is reasonable (d) It may require making some reasonable assumptions in order to calculate the answer (e) It will always be accurate to at least two significant figures.

(e) It will always be accurate to at least two significant figures.

(a) What are the four rules of determining significant figures of a measurement?

1- non zero digits are always significant 2- zeros between two SF are significant 3- preceding zeros are NOT sf 4- trailing zeros are only significant in the decimal portion

You are middle of a large field. You walk in a straight-line for 100 m, then then left and walk 100 more in a straight line before stopping. When you stop, you are 100 m from your starting point. By how many degrees did you turn?

120

Newton's First Law

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

A bullet from a rifle begins to fall

As soon as it leaves the barrel

Suppose an object is accelerated by a force of 100 N. Suddenly a second force of 100 B in the opposite direction is exerted on the object, so that the forces cancel. The object

Continues at the velocity it had before the second force was applied

Which of the following are scalars?

Distance Speed Mass time

speed

Distance travelled per second

A truck is traveling horizontally to the right as in the figure. When the truck starts to slow down, the crate on the (frictionless) truck bed starts to slide. In what direction could the net force be on the crate?

No direction.The net force is zero.

A student's weight displayed on a digital scale is 117.2 lb. This would suggest her weight is

Somewhere between 117.0 and 117.4 lb

velocity

Speed in a given direction

A ball is dropped from the top of a tall building. At the same instant, a second ball is thrown upward from the ground level. When the two balls pass one another, one the way up, the other on the way down, compare the magnitudes of their acceleration:

The acceleration of both balls is the same.

Which of the statements are not valid for a projectile? Take up as positive.

The acceleration of the projectile is positive and decreasing when the projectile is moving upwards, zero at the top, and increasingly negative as the projectile descends.

Precision

The degree to which repeated measurements show the same result.

A golf ball is hit with a golf club. While the ball flies through the air, which forces act on the ball?

The force of gravity acting on the ball

Uncertainty

a numerical value that is assumed to be one or a few units in the last digit in a measurement

What is a vector?

a quantity that has both magnitude and direction

If the force is increased to 50 N in the problem above, how would you describe the motion of the crate?

accelerating

Explain the factors affecting and not affecting coefficient of kinetic friction. Describe. (read the page 93)

affecting- properties such as wetness/dryness, roughness/smoothness, sanded, etc. not affecting- area and speed

displacement

how far an object is from its starting point, including direction

You are riding in an enclosed train car moving at 75 miles/h. If you throw a baseball straight up, where will the baseball land?

in your hand

A person stands on a scale in an elevator. His apparent weight will be the greatest when the elevator

is accelerating upward

A magnitude of a component of a vector must be,

less than or equal to the magnitude of the vector

If the acceleration of an object is zero, are no forces acting on it? Explain.

no, there could be forces still acting on it. two forces of 100 and -100 are acting on a box but canceling each other out

A 50-N crate sits on a horizontal floor where the coefficient of static friction between the crate and the floor is 0.50 and that of kinetic is 0.40. A gradually increasing horizontal force to the right is applied to the crate. How would you describe the motion of the box at the moment force is reached to 20 N.

not moving

If the force is increased to 25 N in the problem above, how would you describe the motion of the crate?

not moving but about to move

Push or pull? Your little sister wants a ride on her sled. If you are on flat ground, will you exert less force if you push her or pull her? Describe. (read page 96).

pull

Acceleration

rate of change of velocity

At time t=0 an object is traveling to the right along the x axis at a speed of 10.0 m/s with acceleration of -2.0 m/s2. Which statement is true?

the object will slow down, eventually coming to a stop

distance

the total length an object has traveled

A rare-wheel drive car accelerates from rest such that all the wheels roll without slipping and start moving to the right. What is the direction and kind of the friction force on rare wheels?

to the right Static friction

If an object is moving, is it possible for the net force acting on it to be zero?

yes

can an object have a zero velocity and a non zero acceleration?

yes, acceleration means you are about to change your velocity

A ball is thrown straight up. What are the velocity and acceleration of the ball at the highest point?

𝑣=0, 𝑎=9.8𝑚/𝑠2 down