30 terms

What is free fall?

When there is no air resistance and gravity is the only thing affecting a falling object.

For a freely falling object dropped from rest, what is the instantaneous speed for the following times? [the end of the 3rd second] [the end of the 7th second]

[30 m/s] [70 m/s]

For a freely falling object dropped from rest, what is the acceleration at the following times? [end of the 5th second] [end of the 9th second] [end of any elapsed time t]

[10 m/s] [10 m/s] [10 m/s]

Toss a ball upward. What is the change in speed each second on the way up? What is the change in speed each second on the way down?

[10 m/s] [10 m/s]

What does the slope of the curve on a velocity-versus-time graph represent?

Acceleration

Calculate the speed (in m/s) of a skateboarder who accelerates from rest for 1 seconds down a ramp at an acceleration of 1 m/s^2.

1 m/s

If a freely falling rock were equipped with a speedometer, by how much would its speed reading increase with each second of fall? Supposed the freely falling rock were dropped near the surface of a planet where g = 17 m/s2 By how much would its speed readings change each second?

[10 m/s] [17 m/s]

(a) When a ball is thrown straight up, by how much does the speed decrease each second? Neglect air resistance. (b) After the ball reaches the top and begins its return back down, by how much does its speed increase each second? (c) Compare the times going up and coming down.

[10 m/s] [10 m/s] [both times are the same]

(a) A ball is thrown straight up. What will be the instantaneous velocity at the top of its path? (b) What will be its acceleration at the top? (c) Why are your answers different?

[0 m/s] [10 m/s2] [the instantaneous velocity is zero, but the speed is changing at a rate of 10 m/s2]

How far will a freely falling object fall from rest in the following times? [four seconds] [eight seconds]

[80 m] [320 m]

How far will a freely falling object have fallen from a position of rest when its instantaneous speed is 18 m/s?

16.2 m

What does the slope of the curve on a distance-versus-time graph represent?

speed

Does air resistance increase or decrease the acceleration of a falling object?

decrease

(a) What is the appropriate equation for how fast an object freely falls from a position of rest? (Use g for the acceleration due to gravity and t for time.) (b) For how far that object falls? (Use g for the acceleration due to gravity and t for time.)

[v=gt] [d=1/2gt2]

Calculate the instantaneous speed and distance fallen for an object that falls freely from rest for 2 seconds.

[instantaneous speed = 20 m/s] [distance fallen = 20 m]

If a freely falling rock were equipped with an odometer, would the readings for distance fallen each second stay the same, increase with time, or decrease with time?

increase with time

How does a vector quantity differ from a scalar quantity?

A vecotor quantity is for direction while a scalar quantity only uses magnitude.

Why is speed classified as a scalar quantity and velocity classified as a vector quantity?

Speed is classified as a scalar quantity because it isn't a direction. Velocity is classified as a vecotr quantity because it measures direction.

If a velocity that is 1 cm long represents a velocity of 16 km/h, what velocity does a vector 3 cm long drawn to the same scale represent?

48 km/h

(a) Calculate the resultant velocity of an airplane that normally flies at 150 km/h if it encounters a 50 km/h tailwind. (b) Calculate the resultant velocity if it encounters a 50 km/h headwind.

[200 km/h] [100 km/h]

Why does a bowling ball move without acceleration when it rolls along a bowling alley?

Becuase there is no force to stop it.

In the absence of air resistance, why does the horizontal component of velocity for a projectile remain constant while the vertical component changes?

Gravity only affects vertical drops.

How does the downward component of the motion of a projectile compare with the motion of free fall?

They are the same.

At the instant a ball is thrown horizontally over a level range, a ball held at the side of the first is released and drops to the ground. If air resistance is neglected, which ball strikes the ground first?

They hit the ground at the same time.

(a) How far below an initial straight-line path will a projectile fall in four seconds? (b) Does your answer depend on the angle of launch or on the initial speed of the projectile? Defend your answer.

[80 m] [It depends on the initial speed of the projectile because in order to solve the equation for distance we need to know the speed.]

Neglecting air resistance, if you throw a ball straight up with a speed of 5 m/s, how fast will it be moving when you catch it?

5 m/s

(a) Neglecting air resistance, if you throw a baseball at 12 m/s to your friend who is on first base, will the catching speed by greater than, equal to, or less than 12 m/s? (b) Does the speed change if air resistance is a factor?

[equal to] [Yes, the speed will be less]

Harry accidentally falls out of a helicopter that is traveling at 105 m/s. He plunges into a swimming pool 4 seconds later. Assuming no air resistance, what was the horizontal distance between Harry and the swimming pool when he fell from the helicopter?

420 m

(a) At what angle from the horizontal should a slingshot be oriented for maximum altitude? (b) For maximum horizontal range?

[90 degrees] [45 degrees]

The hang time of a basketball player who jumps a vertical distance of 2 feet (0.6 m) is 0.667 seconds. What will be the hang time if the player reaches the same height while jumping a horizontal distance of 3 feet (0.9 m)?

.667 s