Exam 4: Forces and Newtons Laws

The only two forces acting on a body have magnitudes of 20 N and 35 N and directions that differ by 80 $\degree$ . The resulting acceleration has a magnitude of 20 m/s2. What is the mass of the body?

You hold a tennis racket in your hand. On top of the racket you have balanced a ball. Which statement is true?

The horizontal surface on which the objects slide is frictionless. If F = 12 N, what is the tension in string 1?

In order to jump off the floor, the floor must exert a force on you:

An astronaut who weighs 800 N on the surface of the earth lifts off from planet Zuton in a space ship. The free-fall acceleration on Zuton is 3.0 m/s2 (down). At the moment of liftoff the acceleration of the space ship is 0.50 m/s2 (up). What is the magnitude of the force of the space ship on the astronaut?

A 5.0-kg mass sits on the floor of an elevator in a Gold Coast skyscraper. The elevator has a downward acceleration of 1.0 m/s2. On top of the 5.0-kg mass is an object of unknown mass. The force of the elevator on the 5.0-kg mass is 80 N up. Determine the unknown mass.

A 1.5-kg object has a velocity of 5 $\hat{\mathbf{j}}$ m/s at t = 0. It is accelerated at a constant rate for five seconds after which it has a velocity of (6 $\hat{\mathbf{i}}$ + 12 $\hat{\mathbf{j}}$ ) m/s. What is the direction of the resultant force acting on the object during this time interval?

Two people, each of 70 kg mass, are riding in an elevator. One is standing on the floor. The other is hanging on a rope suspended from the ceiling. Compare the force $\overrightarrow{\mathbf{F}}_{{F}}$ the floor exerts on the first person to the force $\overrightarrow{\mathbf{F}}_{{R}}$ the rope exerts on the second person. Which statement is correct?

The first of two identical boxes of mass m is sitting on level ground. The second box is sitting on a ramp that makes a 20 $\degree$ angle with the ground. The normal force of the level ground on the first box is NL; the normal force of the ramp on the second box is NR. Which statement is correct?

When an acrobat hangs motionless from a pair of rings:

A high-diver of mass 70.0 kg jumps off a board 10.0 m above the water. If, two seconds after entering the water, his downward motion is stopped, what average upward force did the water exert on him?

An 8.0-kg object rests on the floor of an elevator which is accelerating downward at a rate of 1.3 m/s2. What is the magnitude of the force the object exerts on the floor of the elevator?

A wicket keeper arranges to catch a cricket ball dropped from a height 50 m above his glove. However, his friends substitute a soft 250 g red grapefruit, so that it will smash apart when he catches it. His glove stops the grapefruit in 0.010 s. What force does the glove exert on the grapefruit?

Which of the following is not a fundamental force?

A person weighing 0.70 kN rides in an elevator that has an upward acceleration of 1.5 m/s2. What is the magnitude of the force of the elevator floor on the person?

A 5.0-kg object is suspended by a string from the ceiling of an elevator that is accelerating downward at a rate of 2.6 m/s2. What is the tension in the string?

The horizontal surface on which the block slides is frictionless. If F = 20 N and M = 5.0 kg, what is the magnitude of the resulting acceleration of the block?

A block is pushed up a frictionless 30 $\degree$ incline by an applied force as shown. If F = 25 N and M = 3.0 kg, what is the magnitude of the resulting acceleration of the block?

If F = 5.0 N, what is the magnitude of the force exerted by block 2 on block 1?

A 3.0-kg block slides on a frictionless 20 $\degree$ inclined plane. A force of 16 N acting parallel to the incline and up the incline is applied to the block. What is the acceleration of the block?