Motion

5: Ignoring air resistance, an object falling toward the surface of the earth has an acceleration that is

(A). constant. Objects in free fall are uniformly accelerated by the force of gravity and experience a constant acceleration of 9.8 m/s2. Thus during each second of fall an object experiences an increase of speed of 9.8 m/s.

After leaving the rifle, a bullet fired horizontally has how many forces acting on it (ignoring air resistance)?

(B). One, from the pull of gravity. The force from the gunpowder explosion can act only while the expanding gases can push on the bullet, that is, when it is still inside the rifle. Once it leaves the rifle the only force acting on the bullet is gravity.

Ignoring air resistance, an object falling toward the surface of the earth has a velocity that is

(B). increasing. Falling objects are uniformly accelerated by the force of gravity and all objects in free fall experience a constant acceleration. The acceleration is 9.8 m/s2, so during each second of fall an object gains a velocity of 9.8 m/s. Thus an object in free fall (meaning ignoring air resistance) has a velocity that is increasing during the fall.

A ratio of v/t is a measure of motion that is known as

(C). aThe delta symbol () means "change in," so v means "a change in velocity" and t means "a change in time." By definition, acceleration is a change of velocity per unit time, so v over t describes an acceleration.

A quantity of 60 km/h describes a property of motion known as

(D). magnitude of velocity. The velocity of a moving object tells you the speed and direction of a moving object, sometimes referred to as the magnitude and direction of motion.

An airplane accelerates down a runway at 3.20 m/s2 for 32.8 s until is finally lifts off the ground. Determine the distance traveled before takeoff.

1720 m

A car traveling at 22.4 m/s skids to a stop in 2.55 s. Determine the skidding distance of the car (assume uniform acceleration).

28.6

Upton Chuck is riding the Giant Drop at Great America. If Upton free falls for 2.60 seconds, what will be his final velocity and how far will he fall?

33.1 m and vf = 25.5 m/s

An engineer is designing the runway for an airport. Of the planes that will use the airport, the lowest acceleration rate is likely to be 3 m/s2. The takeoff speed for this plane will be 65 m/s. Assuming this minimum acceleration, what is the minimum allowed length for the runway?

704 m

A car starts from rest and accelerates uniformly over a time of 5.21 seconds for a distance of 110 m. Determine the acceleration of the car.

8.10 m/s/s

A ratio of d/t is a measure of motion that is known as

A). speed. By definition, speed is a measurement of how fast something is moving (magnitude of velocity). It is defined as a change of distance per elapsed time -- or d over t.

A ball rolling across the floor slows to a stop because

A). there are unbalanced forces acting on it. Galileo understood that matter persists in its state of motion, and called the property inertia. Today, we understand that inertia describes the tendency of an object to remain in unchanging motion in the absence of an unbalanced force.

A bike accelerates uniformly from rest to a speed of 7.10 m/s over a distance of 35.4 m. Determine the acceleration of the bike.

Answer: a = 0.712 m/s/s

Rocket-powered sleds are used to test the human response to acceleration. If a rocket-powered sled is accelerated to a speed of 444 m/s in 1.83 seconds, then what is the acceleration and what is the distance that the sled travels?

Answer: t = 1.29 s

A race car accelerates uniformly from 18.5 m/s to 46.1 m/s in 2.47 seconds. Determine the acceleration of the car and the distance traveled.

Answers: a = 11.2 m/s/s and d = 79.8 m