physics test

Josh punches his open left hand with his right hand. Which statement is true about the forces his two hands exert on each other?

Josh's right hand and left hand exert equal and opposite forces on each other.

Two identical blocks, block A and block B, are placed on different horizontal surfaces. Block A is initially at rest on a smooth surface, while block B is initially at rest on a rough surface. A constant horizontal force of magnitude LaTeX: F_0F0 is exerted on each block. After the force has been applied for a time LaTeX: \Delta tΔt, the speeds of blocks A and B are LaTeX: v_AvA and LaTeX: v_BvB, respectively. Which of the following claims indicates the correct relation between LaTeX: v_AvA and LaTeX: v_BvB and provides the best justification for the relation?

LaTeX: v_A>v_BvA>vB . The forces between the atoms in a block and the atoms in a surface oppose the motion of the block and are greater, on average, for block B.

A block of mass M is attached to a modified Atwood machine and is accelerated upward at 3a by a constant force LaTeX: F_0F0. What is the weight of the block?

Mg

Miguel leans against a wall. Which statement is true about the forces Miguel and the wall exert on each other?

Miguel and the wall exert equal and opposite forces on each other.

Jack and Luis are pushing on opposite ends of a shopping cart. At the moment, the cart is staying at rest. We know that the forces each person exerts on the cart are equal in magnitude and opposite in direction. What is the reason this must be true?

Newton's second law tells us these two forces must be equal and opposite.

Three boxes are pulled to the left by strings with negligible mass on a horizontal surface, as shown above. The masses of the boxes are m1, m2, and m3 , where m3>m2>m1>. Friction between the boxes and the surface is negligible. The figure below shows force diagrams for each box. Given that m3>m2>m1, how do the force F and string tensions Ta and Tb compare?

Tb<Ta<F

A 1500 kg car traveling along a road is hit by a 0.1kgrock that creates a small crack in the car's windshield. Which of the following describes the interaction between the windshield and the rock?

The car exerts a force on the rock, and the rock exerts a force on the car. The two forces are equal in magnitude.

Which of the following is a legitimate way to describe the force between a skydiver and the air she is falling through as the skydiver is falling toward the ground?

The drag force exerted by the air on the skydiver

Which of these is a valid force that could be exerted on a car racing through narrow city streets?

The force of friction between the road and the car (its tires)

An object rests on a ramp that is angled at 20º above the horizontal. What direction (relative to the vertical) will the force of gravity point?

The gravitational force will be directed exactly downward, along the vertical.

A spring-loaded launcher has a mass of 0.60 kg and is placed on a platform 1.2 m above the ground. The force of friction is negligible between the platform and the launcher. The launcher fires a 0.30 kg ball that lands a distance D to the right of the platform, as shown in the diagram above. Which of the following explanations is true?

The launcher will fall off the platform and land LaTeX: \frac{D}{2}D2 to the left of the platform because the launcher is twice the mass of the ball.

Consider a car speeding up as it drives along a level road. Which of the following is an action-reaction pair (from Newton's third law)?

The normal force exerted on the car by the road and the downward force exerted on the road by the car.

Imagine standing in an elevator that is moving upward. Which of the following is the most complete list of the forces that belong on your free-body diagram (FBD) in that moment?

The normal force on you by the elevator floor and the force of gravity on you by the earth

An object rests on a ramp that is angled at 20º above the horizontal. What direction (relative to the vertical) will the normal force from the ramp point?

The normal force will be directed 20º to the right of vertical.

A hockey player uses a hockey stick to hit a puck such that the stick provides an applied force on the puck. The puck travels for distance of 0.85 m while experiencing the force from the stick. The puck leaves the stick with a speed of 8.0 m/s and travels at constant speed in a straight line along the horizontal ice for a distance of 12 m. The frictional force between the puck and the ice surface is negligible. Which of the following statements best describes the force or forces exerted on the puck after it is hit by the stick and slides on the ice?

There is no frictional force exerted on the puck, and the gravitational force and normal force are exerted on the puck and are equal in magnitude.

In general, when a car is driving along a straight road, the force of friction between a car tire and the road _____________.

can point either forward or backward, depending on what the car is doing.

Rock X is released from rest at the top of a cliff that is on Earth. A short time later, Rock Y is released from rest from the same location as Rock X. Both rocks fall for several seconds before landing on the ground directly below the cliff. Frictional forces are considered to be negligible. Which of the following graphs best represents the vertical displacement of Rock X as a function of time starting from immediately after the rock is released from rest? Take the positive direction to be downward.

increasing up to the right from 0

An object's mass and weight are _____.

proportional to each other.

Rock X is released from rest at the top of a cliff that is on Earth. A short time later, Rock Y is released from rest from the same location as Rock X. Both rocks fall for several seconds before landing on the ground directly below the cliff. Frictional forces are considered to be negligible. Which of the following graphs correctly shows the vertical velocity of rock X as a function of time? Take the positive direction to be upward.

upside down graph going downward from 0

A 5kg object is released from rest near the surface of a planet such that its gravitational field is considered to be constant. The mass of the planet is unknown. After 2s, the object has fallen 30m. Air resistance is considered to be negligible. What is the gravitational force exerted on the 5 kg object near the planet's surface?

75 N

Three boxes are pulled to the left by strings with negligible mass on a horizontal surface, as shown above. The masses of the boxes are m1, m2, and m3 , where m3>m2>m1>. Friction between the boxes and the surface is negligible. The figure below shows force diagrams for each box. Which of the following is a correct ranking of the normal forces Fn1,>Fn2,>Fn1 exerted on the boxes?

Fn3>Fn2>Fn1

A hockey player uses a hockey stick to hit a puck such that the stick provides an applied force on the puck. The puck travels for distance of 0.85 m while experiencing the force from the stick. The puck leaves the stick with a speed of 8 m/s and travels at constant speed in a straight line along the horizontal ice for a distance of 12 m. The frictional force between the puck and the ice surface is negligible. How does the magnitude of the force exerted by the stick on the puck Fpuck ,stick compare to the magnitude of the force exerted by the puck on the stick Fstick,puck at the time interval in which the stick is in contact with the puck?

Fpuck,stick = Fstick,puck