Exam 8: Force

Three objects are connected by massless wires over a massless frictionless pulley as shown in the figure.The tension in the wire connecting the 10.0-kg and 15.0-kg objects is measured to be 133 N.What is the mass M?

A box of mass 50 kg is at rest on a horizontal frictionless surface.A constant horizontal force F then acts on the box and accelerates it to the right.It is observed that it takes the box 6.9 seconds to travel 28 meters.What is the magnitude of the force?

Consider two less-than-desirable options.In the first you are driving 30 mph and crash head-on into an identical car also going 30 mph.In the second option you are driving 30 mph and crash head-on into a stationary brick wall.In neither case does your car bounce off the thing it hits,and the collision time is the same in both cases.Which of these two situations would result in the greatest impact force?

A woman is straining to lift a large crate,without success because it is too heavy.We denote the forces on the crate as follows: P is the upward force the woman exerts on the crate,C is the vertical contact force exerted on the crate by the floor,and W is the weight of the crate.How are the magnitudes of these forces related while the woman is trying unsuccessfully to lift the crate?

The graph in the figure shows the x component of the acceleration of a 2.4-kg object as a function of time (in ms). (a) At what time(s)does the x component of the net force on the object reach its maximum magnitude,and what is that maximum magnitude? (b) What is the x component of the net force on the object at time t = 0.0 ms and at t = 4.0 ms?

A box slides down a frictionless plane inclined at an angle θ above the horizontal.The gravitational force on the box is directed

Consider a plot of the displacement (x)as a function of the applied force (F)for an ideal elastic spring.The slope of the curve would be

If a 5.0 kg box is pulled simultaneously by a 10.0 N force and a 5.0 N force,then its acceleration must be

A 60.0-kg person rides in elevator while standing on a scale. The elevator is traveling downward but slowing down at a rate of 2.00 m/s². The reading on the scale is closest to

In order to get an object moving,you must push harder on it than it pushes back on you.

Which of the graphs in the figure represents a spring that gets less stiff the more it is stretched?

A 50.0-N box is sliding on a rough horizontal floor,and the only horizontal force acting on it is friction.You observe that at one instant the box is sliding to the right at 1.75 m/s and that it stops in 2.25 s with uniform acceleration.What magnitude force does friction exert on this box?

The figure shows a 100-kg block being released from rest from a height of 1.0 m.It then takes it 0.90 s to reach the floor.What is the mass m of the other block? The pulley has no appreciable mass or friction.

An object is moving to the right,and experiencing a net force that is directed to the right.The magnitude of the force is decreasing with time.The speed of the object is

You swing a bat and hit a heavy box with a force of 1500 N.The force the box exerts on the bat is

A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car.During the collision

Two objects,each of weight W,hang vertically by spring scales as shown in the figure.The pulleys and the strings attached to the objects have negligible weight,and there is no appreciable friction in the pulleys.The reading in each scale is

A dog is standing in the bed of a pickup truck.The bed is coated with ice,causing the force of friction between the dog and the truck to be zero.The truck is initially at rest,and then accelerates to the right,moving along a flat road.As seen from a stationary observer (watching the truck move to the right),the dog

A 1000-kg car is driving toward the north along a straight horizontal road at a speed of 20.0 m/s. The driver applies the brakes and the car comes to a rest uniformly in a distance of 200 m.What are the magnitude and direction of the net force applied to the car to bring it to rest?

You are seated in a bus and notice that a hand strap that is hanging from the ceiling hangs away from the vertical in the backward direction.From this observation,you can conclude that