Physics Exam 2

A 615 N student standing on a scale in an elevator notices that the scale reads 645 N. From this information, the student knows that the elevator must be moving

You cannot tell if its moving up or down

A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector sum of all the forces acting on this crate must point down the ramp.

False

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

False

A box of mass m is pulled with a constant acceleration a along a horizontal frictionless floor by a wire that makes an angle of 15° above the horizontal. If T is the tension in this wire, then

T is greater than ma

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

The force on the truck is equal to the force on the car

Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined plane and allowed to slide down from rest.

The two items reach the bottom at the same time.

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

does not move left or right, but the back of the truck moves towards the dog.

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

exactly 1500N whether the box moves or not

A brick is resting on a rough incline. The friction force acting on the brick is

less than the weight of the block