Physics Exam 2

A sack of potatoes weighing about 200 N falls from an airplane. As the velocity of fall increases, air resistance also increases. When air resistance equals about 200 N, the sack's acceleration is ...

0 m/s2

A falling object of weight 10 N encounters 10 N of air resistance. The net force on the object is ...

0 N

The magnitude of the gain in speed each second for a freely-falling object is about

10 m/s

A bag of groceries has a mass of 10 kg and a weight of about ...

100 N

A tow truck exerts a force of 3000 N on a car, accelerating it at 2 m/s 2. What is the mass of the car?

1500 kg

A jumbo jet has a mass of about 100,000 kg. While accelerating on the runway, the thrust for each of its four engines is about 50,000 N. What is the jet's acceleration?

2 m/s2

A skydiver with a mass of about 100 kg experiences air resistance of about 700 N, and a downward acceleration of about ...

3 m/s2

An object released from rest on Mars requires a time of 1 s to fall a distance of 2 m. What is the acceleration due to gravity on Mars? (Hint: you need an equation that allows you to compute Mars' g when distance and time are given.)

4 m/s2

An object is pulled northward by a force of 10 N and at the same time another force of 15 N pulls it southward. The magnitude of the resultant force on the object

5 N

A person is attracted toward the center of the Earth by a 500-N gravitational force. The Earth is attracted toward the person with a force of

500 N

A falling object of weight 10 N encounters 4 N of air resistance. The magnitude of the net force is ...

6 N

A rock is thrown vertically into the air. At the top of its path, its downward acceleration is ...

9.8 m/s2

Sprinting near the end of a race, a runner with a mass of 56 kg accelerates from a speed of 5.7 m/s to a speed of 7.4 m/s in a time of 2.3 s. The runner produces a backward force on the ground. Of course the ground pushes the runner forward with an equal and opposite force (Newton's Third Law) which accelerates her. Calculate that force.

Find the acceleration by subtracting the two speeds and dividing by the time. Force = mass x acceleration 41N

Two forces (wind pushing with 126 N towards the East and current pushing with 182 N towards the South) act on a sailing boat of mass 87 kg. Compute the boat's acceleration.

Find the force by squaring each force and adding them, then take the square root. Thats the force acceleration = force / mass 2.5 m/s^2

What is the acceleration of a 10.5 kg pail of cement when pulled upward (not sideways!) on a rope by a person with a tensional force of 110 N?

First find mass x 10 (g) then subtract that force from the force given Second divide by the mass 0.5 m/s^2

A firefighter of mass 83 kg slides down a vertical pole with an acceleration of −3.7 m/s2. What is the friction force that acts on the firefighter?

First find the downward force by multiplying the mass by -10m/s^2 Second multiply the mass by the acceleration and then add the force (+) found above 523N

How much acceleration does a 747 jumbo jet of mass 388000 kg experience on the runway when the thrust for each of its four engines is 202000 N?

First multiply the force by number of engines Second divide by the mass 2.08m/s^2

Although Arnold Strongman and Suzie Small in their tug-of-war pull each other with the same force as required by Newton's Third Law, when that force is applied to each one of them, it makes a bigger difference, i.e. produces a larger acceleration, to Suzie because of her having less mass. This is explained by ...

Newton's Second Law

What is the acceleration of a 41 kg block of cement when pulled sideways with a net force of 163 N?

a = F/M 3.9 m/s^2

If an object of constant mass experiences a constant net force, it will have a constant

acceleration.

Hang from a pair of gym rings (but not necessarily symmetrically) and the upward support forces of the rings will always ...

add up to equal your weight.

Arnold Strongman and Suzie Small each pull very hard on opposite ends of a rope in a tug-of-war. The greater force is exerted by

both the same, interestingly enough.

If no external forces are acting on a moving object it will

continue moving at the same velocity.

Whirl a rock at the end of a string on an ice-covered pond and it follows a circular path. If the string breaks, the tendency of the rock is to

follow a straight-line path.

A player catches a ball. Consider the action force to be the impact of the ball against the player's glove. The reaction to this force is the

force the glove exerts on the ball

Which has zero acceleration? An object ...

in mechanical equilibrium moving at constant velocity at rest

Whenever there is an action force (exerted by object X on object Y), there must be a reaction force ( exerted by object Y on object X) which

is exactly equal in magnitude

Before going into orbit, an astronaut has a mass of 59.3 kg. While in orbit, a measurement using the BMMD determines that a force of 122 N causes her to move with an acceleration of 2.1 m/s2. How much body mass did she lose (due to bone loss and change of diet)?

mass = force / acceleration Find the new mass and subtract it from the old to see the change in mass -1.2kg

(In its very slightly elliptical orbit, Earth is closest to the Sun in early January, hence it moves closer in the months before January. Since the difference in distance does not determine the seasons, it must be the tilt of Earth's axis.) During December, when the Earth is moving closer to the Sun, the Sun ...

moves toward the Earth, but a smaller distance.

When the net force on an object equals zero, then ...

the acceleration is zero the velocity could be a constant zero the velocity is constant

Strange as it may seem, it is just as hard to accelerate a car on a level surface on the moon as it is here on the Earth. This is because

the mass of the car is independent of gravity

A rocket becomes progressively easier to accelerate as it travels upward from the ground mainly because

the mass of the rocket decreases as fuel is burned

An object is propelled along a straight-line path by a force. If the net force were doubled, the object's acceleration would be

twice as much