1) A car is moving at 100 km/hr. Its mass is 950 kg. Find its KE.
2) What force is needed to accelerate a 1300-kg car from rest to 20 m/s in 80 m?
3) A 1200-kg car going 30 m/s skids to rest. The friction force is 6000 N. How far does it skid?
1) KE = 1/2 mv^2 = (1/2)(950)(100^2) kg-km^2/hr^2
Not the usual units, but you can do the conversion.
2) 1300 √(20^2/160)
3) a = F/m = 6000/1200 = 5
So, it takes 30/5 = 6 seconds to stop.
s = 30t - 5/2 t^2 where t=6
PHYSICS
To find the answers to these questions, we can use the formulas related to motion and energy.
1) The kinetic energy (KE) of an object can be calculated using the formula KE = (1/2) * mass * velocity^2. In this case, the mass of the car is given as 950 kg and the velocity is given as 100 km/hr. We first need to convert the velocity from km/hr to m/s by dividing it by 3.6 (1 km/hr = 1000 m/3600 s = 1 m/3.6 s). So, the velocity becomes 100 km/hr * (1 m/3.6 s) = 27.8 m/s. Plugging these values into the formula, we get KE = (1/2) * 950 kg * (27.8 m/s)^2 = 364,805 Joules.
2) The force needed to accelerate an object can be determined using Newton's second law of motion, which states that the force (F) acting on an object is equal to its mass (m) multiplied by its acceleration (a), i.e., F = m * a. In this case, the mass of the car is given as 1300 kg and the initial velocity (rest) is 0 m/s. The final velocity (v) is given as 20 m/s. The acceleration (a) can be calculated using the formula a = (v - u) / t, where u is the initial velocity and t is the time taken. In this case, the initial velocity is 0 m/s, and the distance (d) is given as 80 m. Rearranging the equation, we have a = (20 m/s - 0 m/s) / (80 m) = 0.25 m/s^2. Plugging these values into the formula F = m * a, we get F = 1300 kg * 0.25 m/s^2 = 325 Newtons.
3) To find the distance a skidding car travels, we need to use the equation f = μ * N, where f is the friction force, μ is the coefficient of friction, and N is the normal force. The friction force is given as 6000 N. The normal force (N) can be calculated using N = m * g, where g is the acceleration due to gravity (approximately 9.8 m/s^2). Thus, N = 1200 kg * 9.8 m/s^2 = 11,760 Newtons. Since the friction force is equal to μ * N, we can rearrange the equation to solve for the coefficient of friction: μ = f / N = 6000 N / 11,760 N = 0.51.
With the coefficient of friction, we can use the equation v^2 = u^2 + 2 * a * d, where u is the initial velocity (30 m/s in this case), a is the deceleration (which is equal to −μ * g due to opposing motion), and d is the distance. Rearranging the equation, we have d = (v^2 - u^2) / (2 * a). Plugging in the values, we get d = (0^2 - 30 m/s)^2 / (2 * (-0.51 * 9.8 m/s^2)) = 897.06 meters.