Question

a rock is thrown straight up into the air. at the highest point of the rocks path, the magnitude of the net force acting on the rock is
(1) less than the magnitude of the rocks weight, but greater than zero
(2) greater than the magnitude of the rocks weight
(3) the same as the magnitude of the rocks weight
(4) zero
11.
the diagram below shows a compressed spring between two carts initially at rest on a horizontal, frictionless surface. cart a has a mass of 2 kilograms and cart b has a mass of 1 kilogram. a string holds the carts together.
the string is cut and the carts move apart. compared to the magnitude of the force the spring exerts on cart a, the magnitude of the force the spring exerts on cart b is
(1) the same
(3) twice as great
(2) half as great
(4) four times as great
12.
an 8.0 - newton block is accelerating down a frictionless ramp inclined at 15° to the horizontal, as shown in the diagram below.
what is the magnitude of the net force causing the blocks acceleration?
(1) 0 n
(3) 7.7 n
(2) 2.1 n
(4) 8.0 n

Explanation:

Step1: Analyze the force components

The weight of the block \(F = 8.0N\). The net force causing the acceleration along the ramp is the component of the weight along the ramp. Using the formula \(F_{net}=F\sin\theta\), where \(\theta = 15^{\circ}\).

Step2: Calculate the net force

Substitute \(F = 8.0N\) and \(\theta=15^{\circ}\) into the formula. \(\sin15^{\circ}\approx0.26\). So \(F_{net}=8.0\times\sin15^{\circ}\approx8.0\times0.26 = 2.1N\)

Answer:

\(2.1N\) (Option 2)